This list is part of a much longer list that I maintain and sometimes publish.
* 7-ZIP -- Create/Extra ZIP and many other other file compression formats, very powerful. Note can open some installer EXE and MSI files (see Microsoft Orca for more MSI options) (free, open source, Windows, there may be Linux/Mac variants). http://www.7-zip.com/
* CCleaner -- System optimization, privacy and cleaning tool. (free, closed source, Windows) http://www.ccleaner.com/ **Alternate Tool** BleachBit -- Free cache, delete cookies, clear Internet history, shred temporary files, delete logs, and discard junk you didn't know was there. (free, open source Linux/Windows) http://bleachbit.sourceforge.n...
* Greenshot -- Good Screen Shot tool with simple annotation options. (free, open source, Windows) http://greenshot.sourceforge.n...
* IrfanView -- Image Program View, convert, crop, optimize, sideshow, batch Processing etc (free noncommercial, closed source, Windows) http://www.irfanview.com/
Instantbird -- Multi Protocol Instant Messaging (IM) Client - AOL, MSM, Yahoo, etc (free, open source, Linux/Mac/Windows) **Alternate Tool** Pidgin - Multi Protocol Instant Messaging (IM) Client - AOL, MSM, Yahoo, etc (free, open source, Linux/Mac/Windows) http://pidgin.im/
* KeePass Password Safe -- Good Quality secure password manager, stores passwords encrypted. (free, open source, Windows Linux/Mac with Mono) http://keepass.info/
* LibreOffice -- Power-packed Open Source personal productivity suite for Windows, Macintosh and Linux, that gives you six feature-rich applications for all your document production. Excellent replacement for other Office Suites, can open many different and sometimes odd file types -- (free, open source, Linux/Mac/Windows) http://www.libreoffice.org/
* Mozilla.org FireFox -- Web browser for more security then Internet Explore (free, open source, Linux/Mac/Windows) http://www.mozilla.com/ http://www.mozilla.org/
* SpeedCrunch -- fast, high-precision and powerful cross-platform desktop calculator (free, open source, Linux/Mac/Windows) http://www.speedcrunch.org/ & http://speedcrunch.blogspot.co...
* UltraEdit -- Probably the absolute best most powerful text editors around, edit huge files, FTP, column mode, and more (shareware, closed source, Win/Mac/Linux) http://www.ultraedit.com/ **Alternate Tool** Noteppad++ -- Good Text / Source Code Editor replacement for Microsoft Windows Notepad/Wordpad (free, open source) http://notepad-plus.sourceforg...
* VLC Media Player -- One of the best media players out there. Highly portable multimedia player for various audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, mp3, ogg, ...) as well as DVDs, VCDs, and various streaming protocols. It can also be used as a server to stream in unicast or multicast in IPv4 or IPv6 on a high-bandwidth network. (free, oen source, Linux/Mac/Windows)
http://www.videolan.org/