Get rounded corners back on your Mac’s screen
Prior to Mac OS X 10.5, your Mac’s desktop had rounded screen corners. Now you can bring those smooth rounded corners back with Displaperture (say that ten times fast). The developer jokingly notes “enjoy CRT nostalgia” but I think the rounded corners are actually kind of nice looking with the rest of the Mac OS X GUI.
The extent of the rounding is adjustable, from a pleasant minor curve to an utterly ridiculous obstructionist oval that decimates your screen real estate.
If you miss the rounded corners on your Mac display, check out Displaperture.