Metro Run & Walk is THE place to go in Northern Virginia for your running and walking needs. This is where I buy all of my shoes, running accessories, and bars/gels. I used to get my running clothes here, too, but I have enough running clothes to last me into the next millennium!
The staff is very friendly and helpful. They're all runners, so they know what they're talking about. The owner supports a lot of community causes, so I feel good about supporting her store.