Some general points of interest for people who have never been to Hawaii
Maui
> Haleakala (dormant volcano, massive crater and amazing view. pic related
> Lahaina, accessed by (safe & well-maintained) cliff road with an amazing view of the ocean and other islands
> Hana, a dense jungle area with lots of waterfalls and generally a very exotic feel
Oahu
> Honolulu (Main hub & state capital), great for shopping and sight seeing such as the Iolani palace which was the first building west of the Mississippi with electricity and lights
> Waikiki Beach, most popular beach area due to it's location in Honolulu
> North Shore, famous for surf spots and occasionally angry locals
Molokini
> A small atoll with boat and scuba tours, amazing if you want to see vast amounts of reef and sea life
Hawaii (The Big Island)
> Mauna Kea (Active Volcano), might be cool if you really want to see lava since it's very slow moving, be careful not to get trapped in an active flow zone or you're screwed.