I love the Big Island. We stayed for three weeks and divided it into three sections - taking one week to explore each section (west, east and north). I highly recommend downloading the Hawaii The Big Island Revealed: The Ultimate Guidebook to your iPad (or what ever you have) or buy the book. They were pretty spot on with everything and had a lot of great suggestions. Here are my personal suggestions from my trip. I can't wait to go back!
Make your camping reservations in advance. Check the County of Hawai'i website.
From Kona on the West heading South:
Don't miss Pu`uhonua o Honaunau National Historical Park (a.k.a. City of Refuge).
Right next door is Two Step (literally 2 steps from City of Refuge) is truly the best snorkeling ever! It's better then Finding Nemo. A MUST SEE!
Another excellent place to snorkel is Captain Cook Monument. Go down the Napoopoo Rd to the end and you will see kayaks to rent - rent them for the day, it's worth it. Kayak across Kealakua Bay to Captain Cook Monument for another really amazing snorkel spot.
If you want to take a snorkel boat, the Fair Wind Adventure, in the morning, on the Kona side, is a wonderful excursion, they go to Kaleakekua Bay.
Pods of spinner dolphins circle the island. Locals told us that if we are on the water to collect the red leaves of the false kamani tree and give it to them. Dolphins love these specific leaves. I laid the leaves on the water from the safety of a boat and they do play with them like a toy. They are remarkable but do not attempt to swim with wild dolphins. They are federally protected and it's very dangerous.
Check out the Painted Church in Captain Cook. It's really pretty.
The town of Holualoa is wonderful, in the heart of the coffee region and a must-have dinner is a meal at the Holualoa Cafe, it's about 4 miles up the hill from Kona. Wonderful food, especially the meal salads and the lilikoi cheesecake.
Good coffees to buy are Hula Daddy, and Greenwell Farms (in particular its macadamia nut flavored coffee). Drive the Mamalahoa Hawaii, it will take you through Holualoa. Don't miss the coffee plantation tour at Greenwell Farms.
For breakfast, snack/coffee go to Coffees 'N Epicurea in Captain Cook, where they have the best sticky buns, rife with macadamia nuts, I have ever eaten. We went every morning when we were on that side of the island. When I looked it up online it says it is closed. I hope that isn't true.
In Kona, the best place for Mai Tais is the Kona Inn (also excellent coconut shrimp), but my favorite place overall in Kona is Huggo's on the Rocks, for snacks, great drinks and a wonderful view. More spectacular view is from Sam Choy's also in Kona, but the food isn't as good. However, you should try the Spam Musubi there, because they turn something ludicrous into something pretty as well as fun to say you've eaten.
We shopped a lot at Choicemart Supermarket in Captain Cook. The fish was super fresh and they sold local meats at a very reasonable price. We camped on the beach and had fish tacos nearly every night.
Another fun place to eat in Captain Cook is called Teshima's and has been run by the same family since the 1920s. Old lady Teshima, if she is still running the place, is more than 104 years old. Also in Captain Cook, is a good burger joint, Annie's. There is a charming little farmer's market in Captain Cook on Sunday mornings.
We loved getting Tropical Dreams Ice Cream at the Antique Arts Shop in Captain Cook. It's really fun and kitschy.
South at Volcanoes to Hilo and Mauna Loa
Stop off at Punalu'u Black Sand Beach - it's really black sand and a good place to spot sea turtles resting on shore. Remember they are protected so do not touch and keep a safe distance. Pursuit and feeding of marine mammals is prohibited by Federal law.
Don't miss the Southernmost Point. It is really WINDY! I'm surprised the cows can stand upright. At South Point (or Ka Lae) is Green Sand Beach (or Papakōlea Beach.) Extraordinarily beautiful! Go down a dirt road, park at the end of the dirt parking and locals have jeeps to take you up and over to green sands. We didn't feel comfortable with our daughter in their jeep and tried to hike on foot but it's really far. I wish I took the jeep.
Ken's Pancake House in Hilo is a local favorite. "Sumo Size" your dish and see what happens but be prepared to eat a very big portion of food.
Check out Kalani, in Puna, for some of their programs. They have an excellent buffet lunch available to day guests. Puna is very pretty and unusual, it's the Fairfax of Hawaii. Drive the Red Road, it's gorgeous. For local color in Puna, check out Uncle Robert's. Only the locals go here.
Puna is real old Hawaii, very down-to-earth and colorful. The main street of Pahoa is nothing but little independent restaurants. Recent lava flows may have changed the town since I was there. Some shops closed and some remain open.
The farmers markets are terrific - don't miss the Hilo markets, on Wednesday and Saturday. If you are in Hilo, there is a charming little bakery run by a husband and wife counter-cultural young couple who make terrific cream puffs - it's their specialty. Try the passion fruit and the coconut chocolate I think "Puffs" is in the name.
Rainbow (Waiānuenue) Falls is worth the side trip.
Volcano is so interesting and different. Check the Blue Book for great recommendations. I highly recommend buying the inexpensive little guide books at the visitors center. Drive around the main sites of Volcano. Go to the Thurston Lava Tube as early as possible to avoid the tour buses. It is an expensive town but if you head south towards Hilo you will find more reasonably priced places. Beware of steam vents for any lenses you have - cameras, glasses, binoculars, etc.
Volcano has a cute winery worth checking out.
A trip to Mauna Loa is amazing. Stay at the mid way point for at least 1 hour to acclimate yourself. We found 3 geocaches at that midway point and that was a fun way to spend the time. Try to catch the sunset. If you feel sick head back down to the gift shop.
North side from HIlo to Hapuna Beach
Go to the town of Havi for sightseeing, fun souveniring, and make sure to eat at Bamboo, really good food.
Also fabulous - The Blue Dragon on the Kohala Coast in Kawaiahai, a night club supper club, kids are allowed because they serve food. Great line up of music, some of the better cocktails on the island as well. If you go on Sundays you can hear the Olliephonic horns, a big band (18 pieces) who are top musicians.
If you are interested in culinary tourism, check out Hawaiian Vanilla Company, I think they do tours (it's the only vanilla operation in the US at this time).
Waipio Valley is amazing - a strenuous hike but well worth it, pack a picnic and bathing suits, you can enjoy the black sand beach once you get down there.
The resorts are pretty and very well kept but I love camping too much. They do occupy some beautiful stretches of beach in the north well worth exploring.