Desktop Manager
A great feature of the Linux desktops is the ability to have multiple virtual desktops. For some reason OS X doesn’t have such a thing, so I went looking and found Desktop Manager. It’s fast, functional and free. Too much clutter on your screen? Move a few windows off to a separate desktop. And I just can’t get enough of the “Cube” transition.
Between this and Quicksilver I should never have to use that awful Dock again.