Quicksilver (for mac)
“A unified, extensible interface for working with applications, contacts, music, and other data.”
Basically, if you are a bit sick of having to have too many items in your dock, you want to look into getting this.
With the press of a button or two, the Quicksilver interface is brought up, allowing you to quickly access any application or file within seconds just by typing its name. Not only that, it can also act as the finder window by letting you browse through folders using the left and right buttons. Pretty ingenious, huh?
The good thing is that nearly everything is hidden behind the interface. You’ll understand better when you get it, but it’s reduced my dock from about 30 items to 3 when nothing’s open. On top of all this, there are plug ins to let you open applications with macros, control iTunes, and much more I expect. Experiment, the possibilites are nearly endless.