Developer website: Michael Ash
App Switcher is an application switcher for Mac OS X similar to Windows' task switcher, or Proteron's LiteSwitch for Mac OS 9. If you're not familiar with how it works, you press a key combination (defaults to option-tab) which brings up a window with all of your open programs in it. It stays up while you hold down option, and each press of tab advances to the next program. When you release option, the program you selected comes forward. This is a lot like the Dock's command-tab feature. The key difference is that App Switcher orders your programs front-to-back, so that a single press of option-tab always gets you to the program you were in before the current one. Two presses gets you to the one you were using before that, etc. (Jaguar's Dock does a similar thing with your first press of command-tab, but afterwards it goes in the order of your icons in the Dock, which is usually not very useful.) It makes switching quickly between a few programs very easy. App Switcher also allows you to quit, hide, and show running programs from the task window without even bringing them to the foreground. This could be useful for, say, quietly getting rid of that window with the Anarchist's Cookbook while your boss is looking over your shoulder, without letting him know what's going on. There are other uses for this too, of course.
Mac OS X 10.2 or later