I use a few applications...
Quicksilver is a launcher/helper application and has become very very useful for me. Before i used Launchbar which I thought was extremely nice as well but it was either Quicksilver ($0) or Launchbar ($30 i think) so i went with Quicksilver...
http://quicksilver.blacktree.com i don't have the address for launchbar off hand but you can do a search on google for it
Safari is a nice web browser but it's sort of incompatible at my college, so I have Firefox installed as well.
http://www.mozilla.org
I make extensive use of iCal, Word, and MacJournal (for blogging.. i do my writing in this first then post it into wordpress later when it's complete)
A lot of people use Roxio's Toast 6 for their cd burning needs.
I also enjoy using Shrook, it's an RSS reader application for $25, i posted something about this a few days ago in the software forum..
I am looking at doing a full review of all RSS readers i can find and also a full review of all "launcher" applications, (launchbar, butler, quicksilver, etc) in the near future .. i'll of course post the information here. just don't hold your breath as school and the girlfriend take priority.
I just regulary browse versiontracker.com looking for something that will be useful to me.