Most of the activities on Maui are outdoors. In addition to Haleakala, and Hana, there is the Iao Valley.
The surfers hang out on the north side of the island, which is close to the airport. Paia which is on the the north side is a small town with a lot of galleries. The restaurant that the locals want to go to celebrate special occasions is Mama's Fish House, which is in Paia.
A good number of the higher end restaurants are in the Lahaina area.
The beaches are the main attraction on Maui. While each beach has its own charm, I'm partial to the ones on the south side, starting at Kihei and going south through Wailea. The Kihei beaches are the most accessible, unfortunately they all share the same name Kamaole. The locals shorten the name to Kam. The different beaches are designated by numbers, Kam I, Kam II, Kam III, Kam I'v. Kam III is the most popular.
Wailea is an upscale town. The opposite of a folksy artsy town such as Paia. There are a number of large hotels and condos along the beach. Sometimes public parking is squeezed between the condos. The parking looks more like an alleyway. Its worth searching out a parking spot. The locals and tourists like to gather on the beaches and watch the sunset. It is pretty spectacular.
As you head up to Haleakala, there are a number of small towns, where a lot of the locals live, since its noticeably cooler then the beaches. The locals refer to it as up country. Here is where you will find farms and ranches.
Jay