Speaking of my new Nano, I’m very happy with the iSkin I bought for it. I don’t care about whether my iPod gets scratches or dings (as this photo of my old device clearly indicates). I just wanted a belt clip to use while exercising, and this was the only Nano-compatible accessory the store had.
The iSkin is essentially a little condom for your iPod. It’s a rubber sheath that you wedge your device into (heh). It comes complete with a little plastic window that covers your iPod screen.
The belt clip works very well, and the condom would certainly protect my iPod from anything short of a knife fight. However, I discovered one great side effect. One of my frustrations with my old iPod was that I was constantly turning the lock switch on and off, to stop myself from erroneously pressing buttons or the click wheel. The iSkin has the same effect, as you need to exert more pressure to operate the iPod’s controls. Now the lock switch always stays in the ‘unlocked’ position.
The one downside of the iSkin is that my condomed iPod won’t fit into its dock anymore.
DarrenBarefoot.com 
I love Love LOVE my iSkins. Yes, plural. I bought a red one for my video iPod, and I love the hard plastic shell that covers the screen, and the great touch-sensitive skin over the click wheel. I had a nanotube for my nano, but I use the nano exclusively at the gym, and I didn’t like that the port was open. So I got the nano iSkin too. I love how everything is protected! They’re great to deal with too.
I’m really interested in getting a video ipod, but fear that I’d never use the thing.
“The one downside of the iSkin is that my condomed iPod won’t fit into its dock anymore.”
Have you tried lube?