Hawaii is great for hammocking.
One of my favorite places is north of Kona about 3-5 miles. Going along the Queen's highway, right in front of the West Hawaii Veteran's cemetery sign, there is a 4wd road to your left. The road is about 1 mile long, but when you get to the end, there is unpoliced free camping and a 10 minute walk to Makalawena (south). Spent quite a few nights out here, sleeping and waking to ocean sounds, blue water/white sand beach swims in the morning with sea turtles. Amazing.