In Krabi I always stay at the Sheraton Hotel, which has it's own baby elephant on site. You can read independent reviews of the hotel on my favorite travel website,
www.tripadvisor.com. Nice shell covered beach there, and the hotel is located in a mangrove forest, which provides a lot of interesting animal sightings. Beside the hotel are a number of small restaurants, massage places, and travel agencies, and just down the street is a catfish farm/mini zoo, opened by an American woman and her Thai husband. She came to Thailand something like 20 years ago after college, and never went back to the states. At her place you can see alligators, huge catfish, and all sorts of other creepy crawlies.
For an unforgettable island like experience, stay on Railay beach, a roadless peninsula cut off from the mainland by mountains, and drop dead picture postcard gorgeous. There are a variety of lodging options there, from the 600 dollar a night Rayavadee Resort, to 10 dollar a night rooms with cold showers and fan cooling. The slow season lasts through the end of October, so go there while it's still relatively quiet. Activities include rock climbing, island hopping by long tail boat, hiking, monkey spotting, and watching western kids who've been vacationing there a bit too long play with fire sticks at night. Railay beach can only be reached by boat.
For those who don't want take a boat to their hotel, or don't have a Sheraton Budget, stay on the striking Ao Nang beach, also in Krabi. The lodging options there are endless, and the village is really lovely. Rent a motorbike for 250 a day and check out the local. There's a lot to see, and the beach has got to be one of the country's most scenic.