Believe it or not, the seafood restaurant McCormick and Schmick's has a very good Thanksgiving dinner (Yep - turkey, etc...) which was very good when I tried it and is reasonably priced. Also the Old Angler's Inn in Potomac has a delicious, romantic Thanksgiving dinner albeit pricier.
The Washington Times had some Thanksgiving Day restaurants listed in an article 10/25/06 on game, holiday and wine dinners. A few surprises.
Indian tandoori turkey at Rasiki or Bombay Club for a change?
Only a listed few here but early enough to start planning.