Hawaii Visitor's Bureau's WWW pages are an excellent source for information on activities, accommondations (including camping), events and island specific information. Check it out!
Virtually Hawaii includes NASA images of Hawaii and virtual field trips to southeast Oahu and Kilauea Volcano on the Big Island.
Backyard Oahu - Guide to over 80 local trails.
Oahu Hiking Tales - nicely done collection of descriptions on hike on Oahu. A must read page if you plan on hiking on the island!
Hiking Hawaii - provides information and a list of links to Hawaiian Hiking resources on the web.