If you are on Maui long enough to get island fever (or just feel like taking a vacation within a vacation), hop on the Lanai Expeditions Ferry in Lahaina or Ma'alea and take the hour-long ride across the channel to Lanai. The cruise also doubles as a whale-watching adventure in the winter and spring, with sunrise and sunset thrown in as a bonus.
Once the private pineapple patch for magnate Sanford Dole, Lanai is now a sleepy getaway featuring two luxury hotels, snorkeling, mountain biking, and golfing. A shuttle bus (about 10 bucks) runs between the Four Seasons Manele Bay (where you can snorkel with dolphins at Hulopoe Bay), to the quaint (yes, quaint) town square with offbeat shops and restaurants in Lanai City, and winds up further up the hill at the Lodge at Koele, an unlikey Tudor manor with ocean view, arboretum and horseback riding.
You can also rent a Jeep to tour the far-flung beaches (Shipwreck, Polihua) and red-dirt geology (Garden of the Gods), but this will double your expenses and first-time visitors will have plenty to do using the shuttle busses. You'll feel like you've been gone for a week. The Lanai Ferry is you best bang for the buck when looking for a paid adventure when visiting Maui.