I have the ItzKitz for my iPod.
http://www.itzkitz.com/ipod/products.php
It is pretty basic (it can match your iPod's color scheme), it only adds about a half-centimeter of bulk, and it has a detachable belt clip. This thing is POWERFUL. I have thrown it down, dropped it, kicked it, and my iPod has taken a real licking and kept on going. The inside is soft felt so it never scratches the iPod itself. It's got a cover over the screen, so no scratches there either.
For $29.99, you get the case, a headphone winder thingy, retractable USB 2.0 cable, and belt clip. A great deal.
I cannot recommend this case enough. It doesn't look like it's for a kid or a teenager,