There are a good range of Krabi activities and attractions that many people are not aware of, so I have put together a list of the most popular below – in alphabetical order – for those times that you escape the allure of your Krabi.

Canoeing - Many companies around Ao Nang beach and a few at Klong Muang beach offer this service, canoes and kayaks can be rented and are an excellent way to discover the many caves and coves around the Krabi area on your own or with an organized tour.
Climbing - The dramatic limestone cliffs around the Krabi region offer some of the best rock climbing in the world. From beginner to advanced level, everyone can enjoy this pastime - a number of companies around the Ao Nang beach and at Railey Beach area offer full and half day trips.
Cycling - To experience the beautiful countryside around Krabi a good option can be to hire a bicycle. Caution should be taken as the roads can become quite tight but are generally quiet.
Diving - With over 100 islands, Krabi has many exciting undersea sites and teems with exotic sea life. Several companies offer dive trips to the 15 dive sites off Ao Nang -all within a one hour boat ride including a 50 meter long cave at depths of 5-12 meters at Yawabon Island.
Elephant Trekking - A different way to spend a day is to take an elephant trek through some of the lush undergrowth of the local forests. There are a few elephant camps in the Krabi area the best known of which is Nosey Parkers and treks can be easily booked through local agents.
Golfing - Currently there is only one 18 hole golf course in Krabi which is the Pakasai Country Club. There is another 9 hole golf course under construction near the Sofitel Phookethra Hotel.
Sailing - With over one hundred islands Krabi offers some of the most breath taking sailing in Thailand. With one of the many sailing companies around the region you can truly enjoy these local delights. Half day, full day or multiple day trips are available for that unforgettable experience.
Sightseeing - Apart from beautiful sailing around Krabi's 100 islands the area also has a forest national park with a huge diversity of flora and fauna. The cave of Tham Chao Le surrounded by mountains and beautiful islands has prehistoric cave painting depicting animals, people and patterns. The emerald pond in Than Bok Khorani National Park is a beautiful natural lake where visitors can swim, nearby you can visit natural hot springs and waterfalls. Fossils shell beach (Susan Hoi) is a shell graveyard dating back approximately 40 million years ago, and is about 15 mins from Krabi town. There are also a number of temples and monasteries. Wat Tham Suea meaning tiger cave temple is 9 kms from Krabi and is an extremely peaceful temple amidst lush forests and mountains. You can also organize trips to the Phi Phi islands from many of the tour agents, boats leave twice a day and stop at Phi Phi on their way to Phuket, or you can go on an organized tour. There are also a number of popular resorts and good hotels where you can stay on Phi Phi Don (the larger of the Phi Phi islands)
Snorkeling - Amongst the many islands there are some particularly memorable places to enjoy the reefs and sea life particularly around Poda Island. Snorkeling gear can be rented from as little as 150 baht a day along the beach front in Ao Nang, boat and boat trips can be rented at the end of Ao Nang beach front near to the Ao Nang Villa Resort.

I think this list covers most of the major Krabi activities but it is by no means exhaustive, and this fantastic family area of Thailand can offer a lot more than the activities above. No matter what you do you will definitely enjoy your holiday around Krabi.