If you’re in DC on a weekend, especially in the spring and summer, be sure to check out Eastern Market at 7th and Pennsylvania SE. Its one of the oldest continually operating farmers markets in the U.S. and there is more stuff to look at and eat than you can shake a stick at.
On the weekends, they close off 7th street and there are vendors ranging from farmers selling apples to folks selling antique furniture to cute ribbon watches to yummy cookies, just to name a few. Its an easy, fun place to take kids and to be a part of the Capitol Hill community. Its a block away from the aptly named Eastern Market Metro and just a few blocks from 8th Street SE that also has a lot of fun stores and restaurants worth strolling by.
The Market operates during the week too and they have a great cheese shop inside.
Great fun!