Honolua Bay is a my favorite place to snorkel on the island. If you scuba dive you have some wrecks, lave tubes, and Molokini Crater.

Hana has been covered but I will mention there are two ways to get there. I usually drive out the back way which is a little easier and has some cool places to see and then drive back on the Road to Hana. If you can, spend a couple of days in Hana. There are a lot of cool beaches and hikes.

Braddah Hutts near Hana is the best place food truck/plate lunch you can get in all of Hawaii. Seriously, don't miss it.