I know that there's a pretty bitchin' bouldering area at the Giant's Causeway. I've never been there but my friend has. I guess its pretty popular for climbing. Its this big vein of columnar Basalts that stretches from the shore of Ireland to the shore of England under whatever body of water divides them.
Columnar basalts are these perfectly hexagonal rock crystals that stick vertically out of the ground and are all packed tightly against each other. They break off at different levels making a pretty unique looking stretch of coastline. I don't know if the image thing here will work, but type gian't causeway into google images and you'll get a crapload of pics.