I've been using Launchbar from Objective Development for a few weeks now. All I can say is… DAAamn. That's a FINE pice of software. Launchbar indexes all your applications and documents (all configurable) and then gives you access to each of them in as little as 3 keystrokes.

Cmd-shift activates LB, then usually typing the first two or three letters of an application will select it. Hitting enter launches it. Didn't get the right app? Next time, instead of hitting enter, pick the right one from Launchbar's dropdown menu, then hit enter. After that, LB will launch the one you want. It learns, in a surprisingly efficient way, what you want it to do. Rock on!