Spring Point Ledge Lighthouse in South Portland, Maine, is a unique example of an offshore caisson lighthouse that's often opened to the public. The lighthouse was once reachable only by boat, but in 1951 it was connected to shore by a 900-foot granite breakwater.
The Spring Point Ledge Lighthouse Trust opens it on Saturdays during the summer. There are only a couple of open houses left in 2010, including this coming Saturday -- check this site for details.
