Someone in a forum I frequent was reinstalling their computer and asking for a list of should-have programs.
I figure I may as well leave this here for everyone. Mind you this isn't "everything you need" or "anything worth getting that's free", just a short list of what I see as 'the basics'.
Firefox -- opensource, largely secure web browser
* NoScript -- anti-script extension will minimize risk of exposure to malware-infested flash ads. (Tools > Add-Ons > Get Add-Ons > Search "NoScript")
* BetterPrivacy -- Basically like NoScript, but for cookies. (Fair warning this also means having to log to various websites every time you close your browser, as "stay logged in" works through cookies.)
*AdBlock Plus -- Wipes out ads. 'Nuff said.
* XMarks -- far less critical, but a nice extension that allows you to upload your bookmarks and sync between multiple browsers/computers.
OpenOffice -- free opensource equivalent of Microsoft Office. Can leak memory, so don't leave it running all the time, and save & restart the program every hour or so if you're working on something major.
Pidgin -- free opensource IM/IRC client. Very versatile.
MagicDisc /
MagicISO -- MagicISO is a shareware disc image creator, MagicDisc is a freeware virtual drive program for mounting ISOs. Useful for making backups.
VLC / VideoLAN -- free opensource video player.
Combined Community Codec Pack -- Freeware. Make sure to download CCCP and not Insurgent. Codecs to play nearly every type of video/audio file around.
WinRAR -- Shareware. Trial version does not expire and is useful for opening compressed files such as .rar, .zip, etc.
iTunes or
Winamp -- Music player / music libary manager programs. Both good. Winamp lacks the iTunes store and the UI is slightly less intuitive, but is less corporate.
Steam -- Virtual storefront for games with integrated community groups and chat. Steam itself is free, though most games are not.
Paint.NET and/or
GIMP -- art programs, both free. Reasonable alternatives to Photoshop for amateur use. Neither will really replace Photoshop, but consider that Photoshop CS4 retails for >$600 (or ~$200 for college students.) On that note...
Adobe Reader/Flash Player, possibly also Shockwave Player/AIR -- Reader lets you use .pdf files, an extremely common file type for 'published' or 'finished' documents. Flash Player allows use of flash files, increasingly widespread -- shockwave is less common but you're still likely to run into it. Finally, AIR is newer but also utilized by programs such as TweetDeck.
TweetDeck -- potent desktop Twitter application, allows you to split accounts you follow into various groups for easier sorting of information.