For simplicity and ease of use you can't beat the Casio Exilim Z-1000. It's a 10 megapixel camera with outstanding quality. Small, easy to use, and produces some of the most vibrant color ranges I've seen yet.
I've been through three cameras ... Fuji F10, Olympus SP-350, and the Exilim Z-1000 ... and liked the results from all of them. But I think the Exilim provides the best overall color quality of the three.
Other things I like about it ... tiny size (the housing is less than 2/3rds the size of the Olympus housing ... long battery life (can easily get two or three dives out of a single battery charge ... and although the internal flash is reasonably strong (my only knock on the Fuji was a weak flash), the way the diffuser is set up reduces the "hot spot" you get with most cameras.
I got my entire setup (camera, housing, and 2 GB SD card) for $519 at B&H Video ...
... Bob (Grateful Diver)