We just got back from Maui late Thursday night. We've been before, so we had already done Road to Hana and hiked the waterfalls, did a drive around the west part of the island, went to Iao' Needle, etc.
This time we just hung out at the beach by our hotel and only went to Lahaina to walk around once. We stayed in Wailea so we just went to the beach there. We ate quite a bit in Kihei, at Maui Tacos, Shaka Pizza, Sansai sushi and Fred's.
There is a lavender farm and winery on the volcano, plus the volcano itself.
I'd suggest Maui Revealed as a good tour book with lots of off the beaten path type fun stuff!! (hikes,etc)
mama to DD9, DS7 and DD1.