If you ever wanted to make gel-buttons like these, this tutorial takes you step-by-step through it. It's unique for two important reasons; first, it builds a "master button" object that you can alter the colors of without reconstructing–all you have to do is change the RGB values of three of the four objects that make up the button, and second; it uses a vector drawing program to build the object, and not a pixel-based program. Being vector-based, all the components scale up without getting the bad jaggies on the sides.
Go read it here. NB: the demo involves Adobe Illustrator 9, which is three versions back if you're using CS3. It has the master button graphic available for download, but I'd suggest building it from scratch–the steps are quite clearly laid out, and the processes touch on some basic skills that every Illustrator user needs to know.
(NB: illustrations were nicked from the tutorial article. Don't worry, I left the good stuff over there!)