ABC Stores. These things are located like every block in Honolulu and a little more spread out on Kauai. As everyone who's been there or lives/d there knows, they're the one-stop shop for all your tourist junk. However, something I discovered, is that their alcohol is a hell of a lot cheaper than even the grocery stores. I bought a bottle of wine at Safeway, then found the same bottle $5 cheaper at ABC, same thing with Kahlua and Cuervo & margarita mix.
If you're into hiking, consider taking a half-to-full day walk to Hanakapiai Beach. You drive all the way to the end of the road on the north shore of the island, at Haena Beach Park. Park your car (at your own risk) on the side of the road, and you will see the trail head with signage right there. Have water and snacks with you, and sneakers or hiking shoes you wouldn't mind getting muddy.
The trial winds up and down mountain ridges. Don't forget to look at the foilage along the way - the flowers, the plants, the trees and rocks. After trudging up and down the trail, you will suddenly be at Hanakapiai Beach. You need to cross a stream to get there.
When you get there, you will see a large white sand beach. The sand slopes ever so gently downward from the shore, that you can walk far out into the water and still only be shin deep in the water. There are small caves off to the right (as you face the ocean), that you can explore.
Spend as much time at the beach as you want to, then take your time hiking back out. You should be able to do the hike in half a day, or longer, depending on how much time you spend at the beach. The trail is a walking trail, but it does go up and down, and you do need to step over branches and things on the way. The trail is very busy on weekends, so it's safe to go alone or in couples. I wouldn't go alone if there aren't many people on the trail, just for safety's sake.
Grove Farm Homestead Museum is an original Plantation complex that has daily tours. It is very low key and interesting. They even give you a treat of sugar cookies from a wood oven. There is a lot of history here, and beautiful grounds. (808)245-3202
Near Kmart on Nawiliwili Road
Queen's Bath is located on the north shore, it is a large natural pool craved into the lava shelf. It is a marvalous pool to swim in and many fish get in also. It is not safe during high surf.
To get there, follow the trail 25 yards from the end of Kaoplani Road in Princeville. The trail meets the ocean where the small waterfall drops directly into the ocean, go left for 300 - 400 yards. It is recessed in the rock. Use the waterfall on the way back up to rinse off the salt.
Polihale State Park, is the end of the road, take highway 50 from Lihu'e and head west 32 miles to Missile Range, just go through the gate to the guard house, then on a dirt road pass Barking Sands Beach, once at Polihale you will find 15 miles of beach 300 feet wide, with dunes upto 100 feet.
This is where the Na Pali Coast starts, so you can go no further on this side of the island without a boat.
The best place to swim is Queen's Pond, as it is encircled by a small fringing reef, and swimming is good except during high surf. The rest of the beach has no such protection.
Facilities here include shower, picnic tables and water.