UTorrent - Torrent client, faster than Azureus and if you enable the protocol encryption option it will stop your ISP from throttling torrent traffic which appears to be happening with all ISPs these days.
Opera - Fastest web browser available, and the best IMHO
K-Lite Mega Codec Pack - Codec pack that will play every single video file you will ever have. Good excuse to uninstall Quicktime and Real Player (Coz they is crap).