maui kayaks has a great kayak/snorkeling tour.
eat at the Lahaina Fish Company, dinners were great!
go next door afterwards to Kimo's and get a slice of Hula Pie....you have to!
you gotta eat at Mama's fish house also......sooooo good, great atmosphere. go there before sunset to see their own beach.
The Road to Hana is...meh(cause I turned around 10 minutes too soon...doh!). beautiful but long drive. if you do drive it...go all the way to the end which means past Hana to the blowholes and 3 waterfalls. if you are renting a car, make sure its a jeep, driving around you can get into all kinds of places popping that bad boy into 4x4.
There is a great winery there that makes pineapple wine, but you can get it at Costplus world market, so you can skip that if you want.
Definitely get up early and walk the beaches. there are tons of them, obviously.
get ready to drive slow. the island moves slowly. its the way out there.