Ben's Chili Bowl on U Street was highly recommended to us for the half-smoke dog. The line was deep on a Saturday night but moved quickly. They have a large menu with some vegetarian options. Lively atmosphere. It seems Bill Cosby is a fan of Ben's also and has been vocal about it. There was a sign behind the counter which read, "List of Who Eats Free at Ben's : Bill Cosby. No One Else"
Also, Mobys Falafel in Georgetown was great. They make the bread right in front of you and all the ingredients were very fresh and tasty. We were there on Saturday afternoon for lunch and had a great experience. Once we had our food, we had to stand next to the counter waiting for lingerers to vacate one of eight small tables pushed together in a corner of this tiny space. There are other options besides falafel, though we didn't try any of them. Looked and smelled good though!