Windows 7 only: Reader Jay wanted the Windows 7 taskbar to work more efficiently—so he rolled up his sleeves and figured out how to enable middle-clicking to close applications.
Normally when you middle-click on a taskbar icon, Windows 7 opens up a new instance of that application—but that action is also accessible with a Shift+Click as well, so Jay wrote an AutoHotkey script to use the middle-click to close open applications—just like closing a Firefox tab. You can already do this from the thumbnail previews, but this enables the ability on the button itself.
He also changed the left-click behaviour to switch to the last window you were using of a particular application instead of popping up the preview list—clicking more than once will cycle through the list of open windows, and hovering over the button will still show the thumbnail previews. With this feature, you can switch between windows with a single click instead of always being forced into clicking twice every single time—readers should note that even without Taskbar Overlord you can cycle between application windows by holding the Ctrl key and clicking a Windows 7 taskbar button.
Taskbar Overlord is a free download for Windows 7 only, with the AutoHotkey source code available and separate downloads in case you want one feature but not the other. I've been using Jay's script for a week now, and as far as I'm concerned, this option should be built right into Windows 7. Great job, Jay!
Taskbar Overlord [Ocellated]