Halemauu Trail, a lovely path bordered by red and green ferns that winds past volcanic vents, large cones, and ancient lava flows.  In addition to wild goats, hikers may spot the nene, the once-endangered Hawaiian goose that's been designated as Hawaii's state bird.

Sliding Sands Trail, a steep path of ash and cinders that drops precipitously to the crater floor, begins farther up toward the summit, at the visitor's center.

Kaupo Trail, descends from crater to the coast.  The views along the way are stunning, and is a good way to get a good cross-section of the ecological zones on the mountain.