*No regsitry cleaner needed, but I guess portage does a really good job of managing my programs 
Browser - Mozilla firefox
Music - I don't listen to music much on my PC's, but if I did I'd use Audacious or Amarok.
IM program - Pidgin - supports all IM protocols (or Kopete if I'm using KDE)
Media Player - Mplayer
CD/DVD burning - k3b
torrents - Ktorrent (utorrent clone for linux)
anti-virus - clamav (hardly ever use it though)
Office - Openoffice.org
codecs? - I always make sure codec support is compiled in when I compile mplayer, and the necessary codec libraries are always compiled by portage as a prerequisite.
DVD ripping - If I ever needed to I'd probably use something like acidrip.
There are windows binaries available of Pidgin and Openoffice.org if anyone is looking for those types of programs. They do their job really well, and best of all they are free!
