Being able to take screenshots is useful for many reasons, but no matter how practical your reasons, your shots can still be clean and aesthetically pleasing.
If you're a Mac OS X Leopard or Tiger user, you probably know to take screenshots with Shift + Command + 4, which gives you a little cross hair icon to select the area to take a screenshot of. Take that further and press that combo, and then hit the space bar. Instead of a cross hair icon, you'll get a little camera icon.
This enables you to take a perfect shot of one single application (even if it's buried under layers of windows). The resulting screenshot, like the one pictured here, gives you perfect edges, that cool shadow effect, and zero messiness.