Sperlonga Beach! 6 euro train ride to Fungi- 1 euro bus ride from Fungi to Spurlonga = one of the most beautiful beaches (complete with a CAVE). Make sure you walk around the hill town to the other side of the mountain for the superior beach.
Click here for a link to a New York Times article, "Inside Rome." Funny, our neighbor, the Hendrik Anderson Museum (big pink building with odd statues - and a great terrace cafe) made the cut!