given the software sites listed above i'll list what i have onhand instead of links.
MSN Messenger 5.0
Adium (multi software IM chat program, manages MSN, yahoo, ICQ, and
Bittorrent (P2P software)
Azureus (bit torrent GUI/client)
Thoth (newsgroup client, u may oddly have to use a windows machine to get this, from the newsgroups as the SW maker is now out of business, PM me if u are interested or familiar w/ newsgroups)
Colloquy - IRC client
Camino - Mozilla OS X native browser project, like firefox, but better on OS X IMO
Mozilla - Internet suite. Browser/email/newsgroup/IRC clients. i'mplaying w/ this to find out how functional the newsgroup capabilities are.
Shiira -Another browser i'm playing w/, nice so far
Macjanitor - for running the scripts that OS X would run in the middle of the night that help maintain your system
Mplayer OS X 2 - Media Player
VLC - Media Player, 9 times of 10 handles/plays media better than quicktime. essential for anything that isn't an OS X officially supported codec, divx, ogg, xvid, etc...
NeoOfficeJ - Opensource office suite, MS Office compatible for the vast majority of your needs.
Audion - No longer developed by the software maker, but is a nice option for ripping your CDs into MP3s and into choosable names and folders.
iTunes will do the folder bit, but in the actual album folder will only label the songs by number and title. i like to have artist, album, #, and song.
k, well that's all i can think of just now.
hope this helps.