There's not really a whole lot to see or do. If you have a car, you can drive the island, but that will only take a few hours. Go to the lookout on the northern end of the island that overlooks Kalaupapa. Somewhere near there is the 'fertility rock' in all its oversized phallic glory, and it supposedly helps couples who want to get pregnant reach their goals (if the woman sits on the rock, or rubs it). You can drive all the way to the east side of the island, but you just reach a point where the road gets narrower and narrower, so you turn around. Nothing too spectacular other than some nice beach areas. Around the corner from this 'end of the road' is Halawa Valley, which is supposed to be a great hiking area and which contains the longest waterfall in the state, which at one time was named 'Kahiwa Falls'. There is a chance the falls were named after some of my ancestors, since this is a family name that has been passed down the generations, and some of my kin folk are from Molokai. Access to this area is treacherous, so ask the locals about how to get there and how safe it is.
Molokai Ranch is a commercial venture that offers camping / safari / eco-tours for the visitors who are so inclined. I haven't been there, so you'll have to look up their site for more information.
Molokai is not the kind of place to go if you get antsy. It is a very laid back place where you can literally sit in a chair and look at the ocean while drinking the beverage of your choice.
Canoeing is the rage in Hawaii. Rooted in the best maritime tradition of the Polynesians who used to plough the waves of the Pacific from one end to the other, competitions highlight teamwork and strength in a quest for speedy moves across the water. On weekends a visitor might end up seeing a race in the bay of Kaunakakai that has gathered the local fitness lovers and their fans. The competition might include men and women of different ages. Some unexpected “matches” are performed – young bucks challenge seasoned rowers – seemingly done solely for the entertainment of the onlookers. Judging the whole affair appears to be a pleasant business and good excuse for some sunbathing, quite literally.