When you are on Maui you must:
1) Get on a boat and go snorkeling on Molokini (this is a must)
2) Checkout Whalers Village in Lahaina and have lunch.
3) I forget the name of the rain forest on Maui but it receives the most rain in the world and is quite beautiful.
4) Spend a day on Makena Beach (Big Beach), if adventurous hit Little Beach that is connected by a small path for nude sunbathing.