Encryption

13. AxCrypt

The leading open source encryption software for Windows, AxCrypt has been downloaded and registered more than 1.5 million times. It works from within Windows Explorer-just right-click to add encryption to individual files or folders. And it allows you to send self-decrypting files via e-mail, so that the recipient doesn't have to install any software in order to access the file. Operating System: Windows, Linux, Mac.

14. TrueCrypt

Need to protect sensitive files? TrueCrypt can encrypt all or part of your files with very strong encryption algorithms. It's especially helpful if you store a lot of information on a laptop and are worried about people gaining access to that data if it's lost or stolen. Operating System: Windows, Linux, Mac.

File Transfer

15. FileZilla

FileZilla makes it easy to transfer files via FTP. Note that the client version (use if you want to download files from someone else's site) is available for any operating system, but the server version (use if you want to set up an FTP site to make files available to others) is only available for Windows. Operating System: Windows, Linux, Mac.

16. WinSCP

This Windows-only file transfer app supports SFTP and FTP. It includes two different inferface options-one that looks like Norton Commander and one that looks like Windows Explorer. Operating System: Windows.

Desktop Publishing

17. Scribus

Scribus helps users create professional-looking documents for commercial printing (with CMYK separations) or for electronic distribution as PDF files. Feature-rich, it can do most of the things you can do with a commercial desktop publishing programs, like InDesign, Pagemaker, or Publisher, but unfortunately, it cannot open or save documents in other desktop publishing program file formats. Operating System: Windows, Linux, Mac.

E-Commerce

18. Zen Cart

Designed by shop owners and merchants working with designers and programmers, Zen Cart can be downloaded, installed, and managed by anyone with basic computer knowledge. You can set up your product catalog, manage pricing, and more without needing to write any code. Operating System: OS Independent.

Graphics

19. Gimp

Gimp (short for "GNU Image Manipulation Program") offers much of the same functionality as Photoshop. You can use it to retouch photos or create your own images for your Web site, brochures, newsletters, etc. Operating System: Windows, Linux, Mac, Solaris, BSD.

20. Inkscape

An alternative to vector drawing programs like Illustrator or CorelDraw, Inkscape makes it possible to design your own logos and other illustrations. It includes some very advanced features suitable for professional graphic designers, but it is still easy enough for amateurs to use. Operating System: Windows, Linux, Mac, Solaris, BSD.

Instant Messaging

21. Pidgin

Pidgin lets you chat with friends on more than a dozen different IM networks right out of the box, and plug-ins make it possible to connect with just about every chat network in existence. It's also available in more than 70 languages. Operating System: Windows, Linux.

22. Adium

If you're on a Mac, you won't be able to use Pidgin, but you can use Adium, which offers a nearly identical feature set. Operating System: Mac.

23. Miranda IM

This Windows-only chat client's claim to fame is its extremely small size. It lets you connect with multiple networks at once, but doesn't use a lot of system resources and is very fast. Operating System: Windows.

Media Player

24. VLC Media Player

Downloaded more than 41 million times, VLC Media Player's outstanding feature is its flexibility. It can play nearly every audio and video format, and you can even use it to stream video from your own server. Operating System: Windows, Linux, Mac, BSD, Solaris.

Mind Mapper

25. FreeMind

Great for brainstorming, keeping track of projects, or organizing research, FreeMind lets you incorporate text, symbols, arrows, and multiple colors in a document as if you were doodling on a white board or a scratch pad. It's such a unique piece of software that you really have to try it to understand what it can do. Operating System: Windows, Linux, Mac.

Miscellaneous

26. PortableApps.com

If you're going to be traveling, PortableApps.com makes it possible to take all your favorite open-source programs--and your settings and bookmarks--with you on a thumb drive. It includes Firefox, Thunderbird, Sunbird, ClamWin, Pidgin, Sumatra, KeepPass, CoolPlayer, OpenOffice.org, and a couple of games. Operating System: Windows.

Office Productivity

27. OpenOffice.org

If you're considering open-source software as a way to save money, OpenOffice.org is a great option. It includes word processing, spreadsheets, presentations, and databases, plus a drawing program and an app for creating scientific and mathematical formulas. Best of all, it reads and saves in Microsoft Office-compatible formats, so there's no need to spend hundreds of dollars on commercial software. Operating System: Windows, Linux, Mac, Solaris.

28. StarOffice

StarOffice is the same as OpenOffice but with paid support from Sun. If you think you'll need help desk support on a regular basis but don't want to pay the high prices for Microsoft Office, StarOffice might be for you. Prices start at $34.95. Operating System: Windows, Linux, Mac, Solaris.

29. Gnumeric

While it is compatible with Excel file formats, Gnumeric isn't meant to be a clone of any other spreadsheet application; instead, its creators are aiming to make the best spreadsheet available. It offers a lot of advanced features-including some graphing capabilities that many users find superior to Excel. Operating System: Windows, Linux.

30. AbiWord

For word processing only, AbiWord is an extremely lightweight Word-compatible app that offers many of the features people use most often, including mail merge. It's fast and doesn't require a lot of system resources, but it doesn't have as many advanced features as other word processors. Operating System: Windows, Linux, Mac, BSD, Solaris.

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