I now use the griffin reveal backless bumper case. I have tested its effectiveness, dropped it twice so far, one on pavement and once on a hardwood floor, no damage. $30 in best buy, $5-$10 ebay. This thing is great because it has clear sides so it maintains the original good looks of the phone.
I used to use the crimson aluminum case, awesome looking, a bit bulky, but it screwed up my reception.