There's a really neat way to see the Jefferson Memorial on the Potomac River - rent a paddleboat! There's a paddleboat rental station near the Memorial, and you and a friend (I think they fit up to four people) can just float around the Potomac and take in the sites. Be warned, the farther out you paddle, the farther you have to paddle back!
When I went with a friend, we had a great time. We stopped to talk to other paddleboaters and got suggestions on where the good food was that day and where the sales were, etc. It was a bright, sunny day, and the ducks were friendly too.
I hightly recommond trying this!