DTerm is a utility just released by Decimus Software Inc. It's a Leopard-only app that provides a hotkey-triggered HUD which allows shell commands to be run from anywhere in OS X. In case you're wondering why, just imagine what less window switching and screen clutter could mean for productivity on jobs that require both Finder and Terminal. Yes, you can do a lot with Quicksilver, but DTerm provides bash name completion with a dropdown, context sensitivity to your current path and full output with clipboard features. You can also type ???-??? in the HUD to run the command in the Terminal, which will open up to your current path.
DTerm is all about reducing effort, really. The process of running a command in the current directory is reduced to just a few keystrokes and there's no need to grab the mouse or switch to another application. Better Path Finder integration would be nice, but the developers tell me that it's Path Finder's own use of the Accessibility system that prevents that right now.
DTerm requires Leopard and has a free demo (up to 50 commands) after which the program costs $20. Visit the DTerm page for the download and more info, including a speedy video that will satisfy your secret bash-voyeurism fetish and won't waste much of your time.