Ao Nang

Fossil Shell Beach
Thai Su-san Hoi, literally "Seashell Graveyard". Some 7 km west of Ao Nang, this mildly tourist traplikeattraction has slates of compressed 40 million year old shellfish, which bear a small resemblance to concrete. There's also a small grubby museum and a huge slew of gift shops. Entry is a steep 200 baht for foreigners - but only 20 baht for Thais. This tourist trap is simply not worth the 200 baht you have to pay as tourists unless maybe if you are a geology student. As the official Krabi tourism website rather honestly states "most are either engrossed in [sic] this or totally indifferent" (http://www.krabi-tourism....).
Nopparat Thara Beach
Picturesque beach at the western tip of Ao Nang, zoned as a national park. During low tide you can walk up to some of the nearby craggy limestone islands. However ask the locals if it is 'jellyfish season' before plunging in if you are the only one getting ready to take a dip.
Rai Lay Beach
A nice beach near Ao Nang, which can only be reached via a longtail boat. It is actually part of the mainland, but is cut-off by the limestone hills. The beach is cleaner than the one at Ao Nang and Nopparat Thara, and there are some caves worth exploring. There are also hotels and resorts on the beach.

In the off season, it can be a drama to get there! The longtails want 800 baht, so they wait for the required number of passengers. There are two companies who do this, one at the left end of the beach facing the water and the other some several hundred metres to the right. If you do not get a return day ticket you will have to return with the other company. In the off season, from May, there are few tourists and you may have to wait a long time to get the required number of passengers, or pay the 800 baht yourself!