The Sulphur Springs - just south of Soufriere, these hot springs are one of the main attractions on the island. There is a pool that the hot water runs through, so make sure to take your swimming trunks and go for a dip! There are various entrance prices, depending on whether or you want to actually go into the baths themselves or if you just want to go on a tour. Plus, Saint Lucia has a dual pricing discrimination policy, and non Saint Lucians are required to pay about 4 times what the locals pay.
Rainforest hikes - there are several official hiking routes on the island. The Ministry of Agriculture Forestry and Fisheries site has links to information about the ones they support.
Climbing the Gros Piton is an achievable goal for most people. The trailhead begins at an elevation of about 600 feet c. 180m above sea level and requires about two hours of moderate to strenuous hiking to reach the summit of about 2600 feet c. 800m above sea level. A further 1-and-a-half hours are needed to descend. Guides are required and entrance costs USD30. Taxis or local buses can be used to reach the trail head.
Snorkelling is popular and a number of beaches are suitable.
SCUBA diving - done at Pigeon Island, one of the island's Historical Landmarks, as well as between The Pitons, a World Heritage Site. tel. +1 758 484 3346 / +1 758 285 7354.
St. Lucia has become a very popular destination for catamaran sailing. One company that specializes in this is Sea Spray Cruises.
The island has a rather turbulent history. It's worth taking a "Jungle Safari" around the rainforests, as this also includes much information on the island itself.
There is a marine sanctuary national park on one side of the island by the Anse Chastenet resort. Great spot to learn about local marine life & ecology.