I also use Quicksilver. You can customize "triggers" to launch applications. I have Safari set for F1, Mail for F2, iTunes for F3, iCal for F4, and Adium for F5. I have F6 for iTunes previous track, F7 for play/pause, and F8 for next iTunes track.
F9-12 are expose/dashboard. On a laptop, you would need to press fn+[F#] for these to launch.
Probably a little more than you needed/wanted to know, but useful nonetheless.