I just found (around Halloween time) a cool BIG thrift store in the Merrifield area. It's on Gallows Rd. Just north of Arlington Blvd (50) Forgot the name, but it's in a plaza just one block north of Pizzeria Uno and Sweet Water Tavern.
Then, on Main Street/Little River Turnpike in Fairfax is a little thrift shop called "Yesterday's Rose". Again, I only went around Halloween...
but these aren't vintage shops or the like, but traditional thrift stores with you name it under the roof.