Saul Rosenbaum sent us the tip on this one, and he points out that we're a little "Quicksilver centric" around here at TUAW. He's right, we do love Quicksilver, but it's not the only launcher on the block. Launchbar is another good one (and actually, I've been playing with Sapiens a lot lately, so look for a post on that one soon, too).
If replacing Finder with Quicksilver isn't your thing, maybe running GTD apps with Launchbar is more up your alley. Saul has a short writeup on how to get Launchbar running a trigger (he uses "TD") that you can throw short notes into to work with the GTD system. It's a simple process-- since Launchbar already supports shell scripts, you can create a script, hook Lauchbar up to it, and pretty soon you're taking down tasks and notes at a moment's notice.