Haleakala National Park
UPDATE Mount Haleakala now requires a pre-paid ($1.50 per car) parking pass (seperate from the entrance fee) to view the sunrise. You can get your pass here
Haleakala National Park on the first day of the trip most aren't used to the time change. This the best day to drive up for the sunrise at Mount Haleakala. It is a 2-2.5 hour drive from Kihei on a well maintained road, so check sunrise time before leaving and bring a jacket as the temperatures are much cooler at the top. The winding road is well maintained.
The Crater rises to 10,000 feet so it is a pretty spectacular sight. If you were to measure it's height from the sea floor where it starts, it is only 150 feet shorter than Mount Everest (wow). There are hiking trails and horseback riding excursions available.
Don't forget to stop at at Kula and Makawao. Kula has a couple of Floral gardens, and lots of pretty country roads to explore. Makawao is a great little art colony with tons of shops and places to eat.