What is there to do on Bainbridge Island?

Bainbridge Island has become more or less an upscale suburb of Seattle. It has artsy businesses and restaurants, but is mostly residential. Many people on the island work in Seattle and commute via the ferry: http://pnwtravels.hubpages.com/hub/seattle-ferry-t... There is also a bridge across Agate Pass that connects the island to the Kitsap Peninsula. Poulsbo, Chief Sealth's grave and the Clearwater casino mentioned in another answer are all on the Kitsap peninsula - not actually on Bainbridge Island.

There's also Fay Bainbridge State Park. I don't remember it being anything special, but it does have a beach.

And there's the Bloedel Reserve. Just saw a reference, but I can't give a first-hand recommendation.

If you are over 21 there is the Clearwater Casino. [The bus stops within a half mile.] A mile (plus or minus) from the casino is a small Native American museum, and a couple miles more is a marker for Chief Sealth's grave. Paulsbo has some excellent restaurants, and there should be public access to some beaches.

You can also take the local transit buses and just ride around for awhile looking at the scenery.