I really like Eleanor Balaban with Long and Foster's Bethesda office. She helped a first time buyer friend of mine who looked all over the DC metro area finally find a great place in Silver Spring. (And also worked with me when I was a first time buyer and had really solid input on bargaining strategies, which is why I referred her to my Silver Spring friend - she's a nice combination of patient and pragmatic.)
http://www.eleanorbalaban.com/