A short list of great opensource (free, as in freedom) software
Openoffice, like microsoft office but free
Firefox, the best internet browser (from the ashes of Netscape Navigator) with tons of powerful plug-ins
Thunderbird, very good email software (but you need it only if you dont use gmail)
Mwsnap, to take picture of what is shown on your monitor (this one is freeware, not real opensource!)
Vlc Mediaplayer, the best videoplayer around (can read almost everything)
The Gimp, a free alternative to photoshop (almost)
Scribus, a good desktop publishing software
Inkscape, opensource vector graphic editor
Pdf Creator, creates a virtual printer which generates pdf
on your desktop instead of printed paper [just try it!]
Filezilla, a great FTP client and a great FTP server
Scorched 3d, a very nice online multiplayer game in 3D
Freeciv, an opensource remake of Civilization
Poweroff, auto shutdown for you PC (freeware, not opensource!)
7zip, to zip/unzip files
also free to use, but not opensource
AVG antivirus, a good and free to use antivirus software
Spybot, a powerful anti spyware/adware software
and last but not least, my favourite firefox plug-ins
VideoDownloader, to download youtube video on your HD
PicLens, to browse online image gallery in 3D (incredibile, try it on your facebook photo archive)
Web Developer, useful if you know what HTML is…


