I bought a baby blue translucent silicone skin case for my N800 for about $6 on eBay:

http://cgi.ebay.com/Silicone-Skin-Po...d=p3286.c0.m14

First I removed the tilt bracket (very tiny screws).
Next I cut a small square in the side of the case so that with the case on, I can plug in the power and the USB cable. Note that there are already cut-outs for the camera, stylus, headphone and power. Also the entire back is covered.

It not only protects my N800 from being scratched but also it will not slip out of my hand or out of a shirt pocket (when you bend over). Since it is translucent you can see the "D" pad and keys and also the blue alert LEDs.