We stop at the outlets at Perryville, which is a bit less than 1.5 hours away (exit 93 in Md) and about 1 mile from the exit. A handful of outlets, and a tiny playground that consists of the usual climbing structure/slide combo thing. Also a couple of coin operated carasouls/horse rides and the like for tots. Works better to stop on the way home as we don't usually need to stop that soon on the way north. Unfortunately, there aren't really any good food options at the outlets but right at the entrance when you drive in there is a subway/taco bell/dennys.
For when your 1 year old is older, here is a good link:
http://www.washingtonpost.com/wp-dyn/content/article/2008/12/09/AR2008120903059.html