Hanging out for every possible inch of screen real estate? Taskbar Eliminator lets you ditch the taskbar on Windows with a simple keyboard shortcut.
There's not much more to it than that -- it's a single executable, so after you run it, hit Control-Alt-T to set startup options or show and hide via the mouse. Once running, you can hide or restore the taskbar with a simple Control-T. I find the taskbar too useful to want it out of the way for long (and like my Control-T for new tabs in Firefox), but it's a useful utility if you occasionally want to ditch the taskbar.
Taskbar Eliminator is freeware for Windows. For a similar approach with Windows 7, check out Taskbar Overlord. Thanks CC!