Below are a list of the software and utilities which I use and find very useful.
Free Download Manager - FDM accelerates downloads by splitting files into sections and then downloading them simultaneously. As a result download speed increases up to 600%, or even more! FDM can also resume broken downloads so you needn`t start downloading from the beginning after casual interruption. FDM is 100% safe, open-source software distributed under GPL license.
Firefox - Mozilla Firefox is a free and open source web browser descended from the Mozilla Application Suite and managed by Mozilla Corporation. A Net Applications survey put Firefox at 24.07% of the recorded usage share of web browsers as of October 2009, making it the second most popular browser in terms of current use worldwide after Microsoft's Internet Explorer.
Session Manager Firefox Add-on - Building upon SessionStore, this extension allows you to save the current state of Firefox (history, text data, cookies) and return to that state at any later moment. Besides the manually saved states, Session Manager automatically stores the current state in case of a crash.
FlashGot Firefox Add-on - Download one link, selected links or all the links of a page together at the maximum speed with a single click, using the most popular, lightweight and reliable external download managers. Supported download tools are dozens, see http://flashgot.net for details. This extension offers also a Build Gallery functionality which helps to collect in a single page serial movies and images scattered on several pages, for easy and fast "download all".
DownloadHelper Firefox Add-on - Download helper is a Firefox extension to help in downloading media files from the Web. In particular, it is able to store on your disk movie files for which the web site does not provide a "Save File" feature. In addition, DownloadHelper can download, in 3 user clicks, all the image and video files linked from a Web page.
Xmarks Firefox Add-on - Xmarks is the #1 bookmarking add-on. Install it on all your computers to keep your bookmarks and (optionally) passwords backed up and synchronized. Xmarks also helps you uncover the best of the web based on what millions of people are bookmarking.
Highlighter Firefox Add-on - Allows you to highlight text on a webpage by selecting it and clicking 'Highlight' on the popup menu. If you hold down the Shift key while opening the popup menu, a sub-menu appears with more advanced options.
Customize Your Web Firefox Add-on - Customize Your Web (CYW) let's you customize your favorite websites with just a few clicks. What Greasemonkey is for developers is CYW for non-developers. You can remove/rearrange /modify elements, add keyboard shortcuts and do many other things.
Thunderbird - Mozilla’s Thunderbird 2 email application is more powerful than ever. It’s now even easier to organize, secure and customize your mail.
Thunderbird-Tray - Thunderbird-Tray is a system tray launcher tool for Mozilla Thunderbird, the popular e-mail client. You can use TB-Tray to hide Thunderbird to the tray while you don't need it. When you click the tray icon, TB-Tray will restore Thunderbird. It also has a menu of options for quick access to Thunderbird features.
Lightning Thunderbird Add-on - Lightning brings the Sunbird calendar to the popular email client, Mozilla Thunderbird. Since it's an extension, Lightning is tightly integrated with Thunderbird, allowing it to easily perform email-related calendaring tasks.
mailTagger Thunderbird Add-on - an image browser used to insert smileys and images inside a mail in a quick and organized way.
MozBackup - MozBackup is a simple utility for creating backups of Mozilla Firefox, Mozilla Thunderbird, SeaMonkey, Mozilla Suite and Netscape profiles.
Xming - Xming is the leading free unlimited X Window server for Microsoft Windows (XP/2003/Vista). Xming is fully featured, small and fast, simple to install and because it is standalone native Microsoft Windows, easily transported [WWW]portable as a Pocket PC X server. It is totally secure when used with [WWW]SSH and optionally includes an enhanced PuTTY Link SSH client and a portable PuTTY replacement package.
Pidgin - Pidgin is an instant messaging program for Windows, Linux, BSD, and other Unixes. You can talk to your friends using AIM, ICQ, Jabber/XMPP, MSN Messenger, Yahoo!, Bonjour, Gadu-Gadu, IRC, Novell GroupWise Messenger, QQ, Lotus Sametime, SILC, SIMPLE, MySpaceIM, and Zephyr.
Pidgin Guifications - Guifications is a Pidgin plugin that displays "toaster" popups in a user-defined corner of the screen, similar to features that have been added to the official MSN Messenger (now called Windows Live Messenger), Yahoo! Messenger and AOL Instant Messenger clients. It's highly configurable, easy to use, and has theme support. It really is the end all, be all, toaster popup plugin for Pidgin!
Pidgin OTR - Off-the-Record (OTR) Messaging allows you to have private conversations over instant messaging by providing: "Encryption", "Authentication", "Deniability" and "Perfect forward secrecy".
Filezilla Client - FileZilla Client is a fast and reliable cross-platform FTP, FTPS and SFTP client with lots of useful features and an intuitive interface.
Putty - PuTTY is a free software SSH, Telnet, rlogin, and raw TCP client. It was originally available only for Windows, but is now also available on various Unix platforms, with work-in-progress ports to Classic Mac OS and Mac OS X.
TeamViewer - TeamViewer establishes connections to any PC or server all around the world within just a few seconds. You can remote control your partner's PC as if you were sitting right in front of it.
SightSpeed - SightSpeed is the award-winning provider of Internet video chat and voice calling for friends and family, and video conferencing solutions for businesses.
VSee - VSee is a video collaboration software that supports application sharing, desktop sharing, movie sharing, file sharing, USB device sharing, and remote camera control. VSee is designed for scalability and manageability. VSee is extremely low bandwidth, requiring only a fraction of the bandwidth of Skype, WebEx, Polycom, Tandberg, Adobe, Cisco, IBM, etc; and works well over a 3G/EVDO cellular air card.
X-Lite - X-Lite is a fully functioning softphone featuring many of the popular features of eyeBeam. With your existing connection to a VoIP or broadband service or an IP-PBX (e.g. Asterisk, enterprise LAN), it allows you to make calls to any softphone, mobile or landline number.
Microsoft Security Essentials (will not work on pirated windows) - Microsoft Security Essentials (MSE) is a free antivirus software product for Microsoft Windows operating systems that provides protection against different types of malware such as computer virus, spyware, rootkits and trojan horses.
AVG Free is another popular free anti-virus solution available at no cost to home users and provides the high level of detection capability that millions of users around the world trust to protect their computers.
Process Explorer - Ever wondered which program has a particular file or directory open? Now you can find out. Process Explorer shows you information about which handles and DLLs processes have opened or loaded.
DiskInternals Linux Reader - DiskInternals Linux Reader is a program which plays the role of a bridge between your Windows and Ext2/Ext3 Linux file systems. This easy-to-use tool runs under Windows and allows you to browse Ext2/Ext3 Linux file systems and extract files from there.
Another similar tool is Explore2fs but I don't think it works under Vista. Also note that if you are looking for accessing linux partitions as a windows drive for read/write access, these will not provide that facility. There are other ext2/ext3 drivers for windows available for this purpose.
Offline NT Password & Registry Editor - This is a utility to (re)set the password of any user that has a valid (local) account on your NT system.
Eraser - Eraser is an advanced security tool for Windows which allows you to completely remove sensitive data from your hard drive by overwriting it several times with carefully selected patterns.
Virtual Floppy Drive - You can mount a floppy image file as a virtual floppy drive and directly access the contents -- view, edit, rename, delete or create files on a virtual floppy, format a virtual floppy, launch a program on a virtual floppy... almost anything you can do with a real floppy.
WinCDEmu - WinCDEmu makes mounting CD/DVD images simple: double-click on an image file in Windows Explorer and a new drive letter with the mounted image will appear. You can mount as many images as you want at the same time, and you don't need to reserve drive letters when nothing is mounted. WinCDEmu supports ISO, CUE, NRG, MDS/MDF, CCD, IMG formats and runs on all Windows versions from WinXP to Win7.
Alcohol 52% Free Edition is another such program which provides exactly the same functionality but it is not open source. Windows XP also provides its own virtual cd software known as Microsoft Virtual CD Control Panel but it is extremely limited in functionality and does not support copyrighted cds and a large number of image types.
Daemon Tools Lite - DAEMON Tools is an advanced application for Microsoft Windows which provides one of the best optical media emulation in the industry. DAEMON Tools enables you to use your CD/DVD images as if they were already burned to CD/DVD. What differentiates this from WinCDEmu and Alcohol 52% is its ability to backup copyrighted media by creating MDF and MDS file pair (functionality also provided by shareware application Alcohol 120%).
Exaxt Audio Copy - Exact Audio Copy (EAC) is a proprietary CD ripping program. The main differences between EAC and most other audio grabbers: 1. It works with a new technology, reading audio CDs almost perfectly, even damaged or scratched CDs, 2. It successfully reads all the disc, including the pregap which most other software normally ignores and 3. It allows users to set up profiles that allow for individual preferences, encoding in different formats, etc.
Adobe Flash Player - Flash Player is a cross-platform browser plug-in that delivers breakthrough Web experiences to over 99% of Internet users.
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor. It has a nice array of features that include image viewing, management, comparison, red-eye removal, emailing, resizing, cropping and color adjustments. Its innovative but intuitive full-screen mode provides quick access to EXIF information, thumbnail browser and major functionalities via hidden toolbars that pop up when your mouse touches the four edges of the screen. Other features include a high quality magnifier and a musical slideshow with 150+ transitional effects, as well as lossless JPEG transitions, drop shadow effects, image annotation, scanner support, histogram and much more. It supports all major graphic formats (BMP, JPEG, JPEG 2000, animated GIF, PNG, PCX, TIFF, WMF, ICO and TGA) and popular digital camera RAW formats (CRW, CR2, NEF, PEF, RAF, MRW, ORF, SRF and DNG).
Two other very popular image viewers are IrfanView and XnView.
Audacity - Audacity is free, open source software for recording and editing sounds.
MP3Gain - Tired of reaching for your volume knob every time your mp3 player changes to a new song? MP3Gain analyzes and adjusts mp3 files so that they have the same volume.
VLC media player - VLC media player is a highly portable multimedia player and multimedia framework capable of reading most audio and video formats (MPEG-2, MPEG-4, H.264, DivX, MPEG-1, mp3, ogg, aac ...) as well as DVDs, Audio CDs VCDs, and various streaming protocols. It can also be used as a media converter or a server to stream in unicast or multicast in IPv4 or IPv6 on networks.
Further it has a volume enhancing feature which can increase the volume to 400% (extremely useful for laptops in which the playback sound is low).
QuickTime - QuickTime is a multimedia framework developed by Apple Inc. capable of handling various formats of digital video, media clips, sound, text, animation, music, and several types of interactive panoramic images. Available for Classic Mac OS, Mac OS X and Microsoft Windows operating systems, it provides essential support for software packages including iTunes, QuickTime Player (which can also serve as a helper application for web browsers to play media files that might otherwise fail to open) and Safari.
RealPlayer - RealPlayer, briefly known also as RealOne Player, is a cross-platform media player by RealNetworks that plays a number of multimedia formats including MP3, MPEG-4, QuickTime, Windows Media and multiple versions of proprietary RealAudio and RealVideo formats.
Editors And Viewers
Notepad++ - Notepad++, a source code editor and MS Windows Notepad replacement, has the mission to offer a greener environment. By optimizing its routines, it results in reducing CPU power consumption then reducing the world carbon dioxide emissions.
Notepad++ Autosave Plugin - AutoSave allows to automatically save the currently open files based on a timer schedule (default is 1 min) and/or upon the application losing focus. The plugin offers a couple of options to save the current (or all the files), selecting only the named ones, accessible through a menu.
There are several other plugins offered by Notepad++ in the Plugins page which may be useful to you.
Adobe Reader - Download free Adobe Reader software to more securely view, print, search, sign, verify, and collaborate on PDF documents, online as well as offline, from your home or office.
Foxit Reader - Foxit Reader is a free PDF document viewer and printer, with incredible small size (only 2.1 M download size), breezing-fast launch speed and amazingly rich feature set. Foxit Reader supports Windows 98/Me/2000/XP/2003/Vista. Its core function is compatible with PDF Standard 1.7.
LibreOffice - LibreOffice is a free and open source office suite, developed by The Document Foundation, which began as a fork of OpenOffice.org. It is largely compatible with other major office suites, including Microsoft Office, and is available for a variety of platforms.
Word Viewer - View, print and copy Word documents, even if you don't have Word installed. This download is a replacement for Word Viewer 2003 and all previous Word Viewer versions.
Excel Viewer - Open, view, and print Excel workbooks, even if you don't have Excel installed. This download is a replacement for Excel Viewer 97 and all previous Excel Viewer versions.
PowerPoint Viewer 2007 - Microsoft Office PowerPoint Viewer 2007 lets you view full-featured presentations created in PowerPoint 97 and later versions.
Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats - Open, edit, and save documents, workbooks, and presentations in the file formats new to Microsoft Office Word, Excel, and PowerPoint 2007.
BullZip PDF Printer - The BullZip PDF Printer works as a Microsoft Windows printer and allows you to write PDF documents from virtually any Microsoft Windows application.
MD5sums - MD5sums calculates the MD5 message digest for one or more files (includes a percent done display for large files). By comparing the MD5 digest of a file to a value supplied by the original sender, you can make sure that files you download are free from damage and tampering. MD5 values are frequently supplied along with downloadable files.
Memtest86+ - Memory Testing Tool
Tray It! - TrayIt! allows to save precious Taskbar space for minimized windows. For each application which applies TrayIt! it creates a small icon in the System Tray. (System Tray area is located near the Clock). When application's window is minimized this icon represents the application on the Taskbar instead of the regular "minimized rectangle". It is particularly useful for background tasks you typically keep running on your PC all day long like your favorite E-mail client, Real Player, etc..
Wordweb - WordWeb is a free English thesaurus and dictionary for Windows, and can be used to look up words from within almost any program in just one click. It works off-line, but can also look up words in web references such as the Wikipedia encyclopedia.
7-Zip - 7-Zip is a file archiver with a high compression ratio.