Things we've done there:
Parasailing
JetSkiing
Helicopter ride over the volcano (dormant) and West Maui mountains.
Shopping in Lahaina - a mix of tourist traps, restaurants and art galleries.
Pride of Maui Snorkel to Molokini.
Atlantis Submarine ride. Kind of boring for divers but wave at Tim (Kidspot here) he's the diver on some rides
Golf at Wailea or Kapalua. Both have hosted major championships.
The Maui Ocean Center is definitely worth a look. About the only place you can reliably dive with Tigers.
The Grand Wailea in Kihei is a 5 star hotel built on a waterpark. There's about a dozen pools, including one they whitewater raft in.
Old Lahaina Luau
I liked the atmosphere of the boardwalk/restaurants up in Kaanapali. Good food and a great view.
Things we've not done:
"Mountain biking" - which btw is all downhill if you do the Volcano ride.
Backcountry hiking to some amazing waterfalls.
There's a new(ish) zipline ride in the mountains.
The drive to Hana is an all-day thrill ride.
Sportfishing out of Maalea harbour.
Trilogy or one of the other fast Catamaran rides.
Whale Watching in the Spring.
I cant believe everything closes down by 9:00 - 1:00am.
?? It's not a big club area although there are some. For that you want Waikiki...
Might be interested in this:
Maui Hawaii Harley Rentals, Maui Motorcycle Rentals, The Aloha Toystore