dermaSHOT Silicon Case for iPhone 3G/3GS - Little Blue Box Blue
Reduced from £19.95. Free super saver delivery.
Haven't tried it but got a good review at http://www.tipb.com:
"The case fits really well around the iPhone 3Git is made out of a softer silicone material that wraps solidly around the iPhone yet offers a certain tactile feel that most other rubber cases do not. Specifically, the case feels soft and has a certain amount of depth to it, theres a give to the case unseen in most rubber options. The extra grip that the case offers is a great touch and really feels good in hand."