One: Twin Falls Botanical Preserve, at the beginning of the Hana Highway, is on the tourist radar, but you can find places to call your own. There are actually a half-dozen falls with swimming pools, most of which visitors never see.
Two: Baldwin Beach Park on windward Maui near Paia is the perfect place to hang out—beachcombing, surfing, snorkeling, and surfing all combine to say aloha.
Three: Where the resort strip ends in West Maui just north of Kapalua is the Honolua Marine Preserve. Tour boats bring paying customers, but it's easy to get there on foot. As a bonus, you can watch surfers ride one of the better waves in the Islands off the point (from which this photo was taken).
Four: Ka'anapali Beach still has the buzz carried forward from its heydays in the 1970s, when it was called Dig Me Beach. Yeah, baby. Black Rock, right in front of the Sheraton, attracts jumpers all day long, and the snorkeling is good. A beach path along the resort strip's gardens and pools provides an opportunity for excercise while people watching.
Five: Lahaina was Kamehameha's choice for the capital of the islands. The king's big footprints, along with historical thread from the missionary and whaling periods, are evident along the town's quaint streets. Bars, restaurants, and shops make the place hop. All sorts of tour boats depart from the harbor, along with ferries to the neighboring islands of Lanai and Molokai.
Six: Haleakala National Park is lofted at 10,000 feet. Its Red Hill Summit viewing kiosk attracts a throng of sunrise seekers, but this is a chilly proposition. Try sunset. The Sliding Sands Trail into the crater (technically an eroded valley) is the park's centerpiece, but remember when hiking into all that magificance that you need to hike back out.
Seven: Iao Valley State Park in Wailuku gets hammered with tour buses, and most visitors walk the steps to see the signature Iao Needle. There's room to roam in a botanical garden, as well as on an unsigned trail that departs the park at the Needle to a spectacular viewing spot in the adjacent state forest reserve.
Maui Trailblazer has details on visiting all of Maui's well-known wonders, as well as place to call your own for the day.