(Merged the two threads since they both had responses)
I've been to Kaua'i once. Was absolutely amazing. There are so many little differences from the mainland US that it feels like a weird foreign country where you recognize everything.
http://en.wikipedia.org/wiki/Kauai
The most interesting and unforgettable things from there was the scenery, weather, and geography. And the chickens. Those damn chickens.
See, the chickens on Kaua'i are endangered because they are such a small population. But, they have no natural predators on that island, and since it's actually ILLEGAL to kill one (even accidentally), they have the run of the island. If one decides to sit down in the middle of the road, you stop and wait (while trying fruitlessly to shoo it away).
The weather is pretty much the same temperature year-round (compared to the Carolinas, it's the same!), but rain can happen whenever it wants. Like, it's really sunny with a few clouds, and BAM big rain. And then... it stops 1 min later and it's all sunny again. The locals aren't even phased when the rain hits. Also, don't expect any air conditioning, cause there are probably like 5 places on the island that have it.
And speaking of rain, the mountain in the center of the island is one of the wettest places on the world. But the coolest part is that it's the center of the volcano-mountain that is the wet place... kinda like a giant birdbath. Because of all the water that sneaks out and over, waterfalls happen ALL THE TIME on it... if you can see the mountain through the almost permanent clouds around it. Even cooler, the waterfalls seem to move from one spot to another, so you could be admiring one in the morning and 6 hours later, that waterfall is gone and another has popped up somewhere else. http://en.wikipedia.org/wiki/Mount_Waialeale
The northern and western part of the island are the really great spots, if you can reach them. See, most of the population is on the south and eastern part of the island and no usable roads are on the western side. The ginormous national park makes sure of that, but there is an epic hiking trail that goes along the western edge that I tried.
The southern side has a freakin CANYON on it. It's not small either. According to wikipedia, it's 3000 feet deep (the mountain is only 5,200 feet tall). The drive along the canyon edge is actually pretty dangerous; we needed to take turns driving due to the stressful concentration! The climate is like night and day compared to the rest of the island. http://en.wikipedia.org/wiki/Waimea_Canyon
Great trip.