Underwater Cases
Most manufactures also make underwater cases for their cameras so that you can take the camera underwater.
Memory Cards
Always worth considering buying an extra high capacity one because a camera usually only comes with a 16MB memory card, allowing only about 10 photos to be taken.
Cases
Soft carry cases are most popular for protecting the camera from scratches while being taken around.
Neck Strap
A neck strap is very useful for having your camera ready to go by hanging down from your neck.