well whaddya know...im typing from a macbook myself.
-adium is a good choice for an IM program as its very clean and uses AIM, ICQ, Yahoo, and basically any other IM client all in one
-inquisitor for safari - excellent/improved built-in search
-firefox/camino (mac only)
-synergy (handy program to show you what song is playing)
-transmit (ftp client)
-vlc (to play the formats mac cant recognize)
-roxio toast titanium (great for making backups and burning cds/dvds)
-macstumbler wi-fi finder
-transmission (for torrents)
-stuffit expander for zip, rar files
-windows media player...since i dont think there is any other way to play .wmvs...
hope that helps!