Derrynane House is an interesting place to visit. Derrynane House was the home of Daniel O'Connell who was a lawyer and politician (born August 6th 1775). O'Connell was instrumental in the movement to win political rights for Irish Roman Catholics (forming the Catholic Association in 1823). For his acts that helped Catholics around Ireland he is known as 'The Liberator'.
Entry costs €2.75 and you get an information sheet on all the rooms of the house (available in English, Irish, French, German, Italian, Spanish and Dutch) - many contain impressive gifts from statesmen and religous leaders (as 'thank yous' for his work). Guided tours are available on request. There is also an audio visual presentation that goes for about 25mins.
Plus if you're feeling hungry there is a nice little cafe at the house.
Be sure also to take the short walk down to the beach, it is a nice beach and the surrounding scenery is beautiful (picture of the beach in my Kerry travelogue)