I can look up the obvious things, and that’s cool, but are there any other off-the-beaten-path things I should try to work in (like the Green Sand Beach)? I’ll be traveling a lot on the Island, so it doesn’t have to be in Hilo.
If you look hard enough, you can see not only a green sand beach, but a black and red sand one too.
The guidebook is Hawaii: The Big Island Revealed. It has all sorts of off-the-beaten-path things to do.
If conditions are right, the adventure that puts all the others to shame is the hike to the Pu’u O’o volcano vent (where the lava emerges from deep underground). This is a difficult-to-find and moderately strenuous hike (the above guidebook is essential). You must have a tradewind day to avoid hazard from the fumes. The hike to the edge of the lava field is about 2.5 hours one way, depending on recent rain (walking sticks recommended). Even this guidebook recommends you stop there.
If you decide to continue, the hike across the lava field is about 40 minutes via a trail that’s sometimes hard to follow and undeniably treacherous. The crater itself is seriously hazardous. But the views of lava emerging from the earth are more than worth the effort and risk, IMO. [Disclaimer: I last did this hike 4 years ago.]
Another interesting adventure is the drive to the Mauna Kea summit. Despite what you may hear, it’s not a problem for an ordinary 2-wheel-drive vehicle if the driver is semi-competent.
Getting to the Capt. Cook monument at the north side of Kealakekua Bay is not easy, but the snorkeling there is probably the best on the island.
Xema’s response looked familiar. Not only do I agree with him, he and I both responded to a previous thread on this subject.
Here it is:
http://boards.straightdope.com/sdmb/showthread.php?t=240349&highlight=hawai'i
My son and I were there during the last week in August. Great time.
He caught a 173 1/2 lb blue marlin. Kona has what I think is the best sportfishing in the world.
We also did snuba diving. That’s when you have a regular scuba regulator mouthpice but there is a 25-foot hose that runs up to an air tank on a raft.
We were supposed to go on the Atlantis submarine but they took it out of service that day for some maintenance.
On a previous trip we took a helicopter ride around the island and over the volcano…following the lava down to where it spilled into the sea. Very, very neat.
I’ve been to Hawaii 4 times now. As far as I’m concerned, I wouldn’t spend another moment in Honolulu. The North Shore of Oahu is pretty cool, but the Big Island is my favorite.
Here’s hoping you have a good time.
See about finding a nice natural hot spring or sauna to hike to. Mah I loved those. Of course don’t go alone.
If you want a sort of “Lost World” experience, hike through Waipio Valley and over the hill to Waimanu Valley. Its not an easy hike, but its not too difficult either. Its too far to walk in and out in a day so you’ll need a camping permit.
Waipio is pretty interesting, but its inhabited. Waimanu, on the other hand, hasn’t been inhabited for many years. There are ancient Hawaiian home foundations as well as lots of fruit trees that were planted at the time the Hawaiians lived there. The beach is nice and you should also walk toward the back of the valley. You’ll probably be the only one there, but its so isolated a little company isn’t a bad thing.
Two words: Kona coffee.
…and pretty please bring back some for me?
These may qualify as the obvious things, but in case they don’t:
I spent almost an entire day and about 5 rolls of film at the Hawaii Tropical Botanical Garden back in 1990 or 91; I still enjoy looking at those pictures 
Oh, and another two days in Hawai`i Volcanoes National Park; I ended up almost ruining my camera there because of an amazing downpour that came out of nowhere, but it was still worth it
Enjoy your trip!
Definitely do the helicopter ride over Kilauea. And assuming you’re sitting at the window, ask the pilot if he’d turn the copter 90 degrees sideways, so you can get a good shot looking down at the lava.
And if you’re going to the place where the lava pours into the ocean, go at night, and don’t forget to bring a flashlight.
I second the Hawaii Tropical Botanical Garden. Whenever I’m having my blood pressure checked, I close my eyes and think of that place, and my BP decreases.
Also, there’s a tour that takes a van-load of people up to the observatories on Mauna Kea at sunset, then a star-gazing party.
Waimea is pretty cool, too.
I’ve alse been to that park in the southeast section of the Island. It’s not so great.
Anyway. . .for how popular The Big Island Revealed is, a lot of the spots he talks about are completely unpopulated. If you leave your car next to the road, and walk a mile to the beach over some rough trails, you can have an entire beach to yourself there.
To wit, a small photo album.
Pictures 1, 2, and 6 were from beaches we had entirely to ourselves, except for maybe 2 other people. 2 is a black sand beach.
If that link doesn’t work, then whatever. I don’t really have much in the way of photo sharing on the web.
EDIT: waipio valley. waimea is the region.