South Coast of the Big Island of Hawai’i
The big destination on the south coast of the Big Island of Hawai’i is Volcanoes National Park and Kilauea volcano. However the south shore of the Big Island deserves a day of touring all on its own.
There is a green sand beach to see at the end of South Point Road, the small town of Naalehu is a great place to stop for a snack or lunch, there is a lovely black sand beach where you have a good chance to see sea turtles, and if you are really lucky, you might see an active lava flow!
Getting there
From the Kona area to Volcanoes National Park is 87 miles. The first 30 miles of road is a two lane highway winding it’s way along the slopes of the Kona coast. This first section will take you most of an hour ( with no stops), traveling at only 30 mph to 50 mph. Take your time, since some of this road is quite hazardous, with sharp turns and hidden intersections. Once you leave the South Kona area, and start heading east along the south coast of Hawaii toward Kilauea, the speed limit increases, and the road becomes mostly straight. Coffee and macadamia nut plantations abound in this area, especially while we are still near the Kona area. The South Coast begins as we pass Ocean View, the last gas station until Hilo, so fill up!
The sights
The highway lookout near Hawaiian Ranchos offers a spectacular view of the southwest coastline. If the wind is very strong, this is the part of the coast is where you will first encounter it. South Point Road is next, where you can find the famous green sand beach. Read your car rental agreement before proceeding, since some rental companies forbid you driving their vehicles on this road.
The small town of Naalehu is next. Mark Twain stayed near here, writing about Hawaii as it existed over a hundred years ago in his excellent book “MARK TWAIN’S Letters from Hawaii” (edited by A. Grove Day, University of Hawaii Press, ISBN 0-8248-0288-8). Available in paperback from most bookstores. The book makes a good read, if you are interested in bits of history of Hawaii at the time when the islands were still called the Sandwich Islands. Mark Twain climbed all around Kilauea Volcano, and reputedly planted a Monkey Pod tree in Waiohinu (the town just before Naalehu), however the tree blew down in 1957.
When I traveled this coastal highway in January 2001, Honu’apo Bay & Pu’u o Ka’au were really taking a beating with the wind. The surf was crashing hard against the rocks. There is a good view of the coastline from the highway lookout. 
Punalu’u Black Sand County Beach Park is worth a stop, since it is perhaps the most accessible black sand beach on the Big Island, there is lots of parking, and it is easy access to the beach on foot. The bonus is that sea turtles are often to be found on the sand sunning themselves.
The Hawaii Belt Road (55 mph) will take you past the entrance to Volcanoes National Park. I won’t discuss this further here since this destination requires all day (ideally more than one day) to fully experience. Instead, we drive further along the highway heading east to the little community of Volcano, which makes a good rest stop.
Pāhoa is the next little community (right turn off the highway onto route 130), and although it is surrounded by natural reserves, the area is generally unremarkable and not really worth a stop. The only interesting sight to see in this area is if you follow highway 130 through Pāhoa backtracking in a southwest direction towards the eastern limits of Volcanoes National Park to the remote community of Kalapana. Now you will see the devastation of volcanoes up close, and if you are lucky as I was in 2009, you just might see active lava flowing into the ocean in this area!
At this point, you are at the eastern limit of the South Coast of Hawai’i. Either you turn around and drive for almost two hours back to the Kailua-Kona area on the west coast, or you carry on for another half hour and drive into Hilo on the east coast.