DC was a blast. I had a lot of fun there and time went by way too quickly.
DC is very veg*n friendly with several veg*n restaraunts in the area. There are also several health food stores there, and a lot of the restaraunts that served meat as well had knoledgeable staff that knew what was in everything and helped with making sure the items were vegan friendly.
Pangea is also located just outside the city limits and right off the subway line. It is a small storefront with the warehouse in back. So if you are in the DC area, you can go there and save the shipping costs. I ended up spending $120 there. Also if there is something that they do not have up front do not be afraid to ask the helpful staff, they will gladly go back and get whatever you need (really nice that the warehouse is right there).
If you go to the Smithsonians, it is best to eat at the Native Americian one, they have a better selection of food than the other ones, and it was really good and decently priced (for touristy type of places).
You can read more about my adventures in DC and see pictures in my blog at http://whogivesacrap.net. You do need to register though, but there is no cost or commitment.
George W. Bush