Union Market (1309 5th Street)
Crafty Bastards is an annual arts and crafts fair organized by the Washington City Paper. You can find everything from unique t-shirts, to really cool prints that re-write history (e.g. a giant snake attacking the Washington Monument), to faux taxidermy.
Kids get in free, and tickets are $5 at the door for adults. You can score 2 for $5 online if you buy them today.