It seems that everyone has their favorite app launcher/wonder app these days whether it be LaunchBar, Quicksilver, or Butler. If you still haven’t found the app launcher for you, and you enjoy bowler hats, might I suggest you check out Alfred?
Now in beta, Alfred (something tells me the developers are fans of Batman) allows you to launch applications and search the Web, Amazon, IMDB, and more all with a few keystrokes. Assign a hotkey combination, and pressing those keys will bring up a query window. Type in the first few letters of the application you want to launch, or use a keyword to perform a Web search, and you’re off. Alfred will drop down results as they are found. If the first result is the one you’re looking for just hit return, and it is launched. If what you’re looking for is further down the list of results, Alfred very helpfully assigns a specific command key combination to each result. (The combos start at Command + 1 and go from there.)
If you're thinking of switching from one of those other quick launchers, keep a couple things about Alfred in mind: the application is in beta, and the Alfred search works differently than that of Quicksilver (the biggest difference being that it is a strict textual search, so "ff" won't find Firefox).
To get in on the Alfred beta you have to sign up with your e-mail address, and the Alfred team will send you a message with a download link. Alfred requires OS X 10.5 and later.