If you aren't going to DC on Saturday - or even if you are, and you want something to do on Friday evening or Sunday, the annual Delaware Saengerbund Oktoberfest is my favorite local festival:
http://www.delawaresaengerbund.org/September 14, 15 & 16, 2007
Under the Big Tent -- Rain or Shine
49 Salem Church Road, Newark, Delaware
Contributions to the table pyramid are always welcome...

The best parking is always at the mosque across the street on Sunday. I love this country - where else does a mosque provide parking for a German beer drinking festival?