You could try HalalCo in Falls Church. Lots of people like it -- it's certainly huge, but I don't really like the produce/meat there. I go to A-1 India Grocery at 4815 Lee Hwy, Arlington for quick trips, but my preferred market by far (worth the trip IMO) is Ginger & Spice Market at 6548 Little River Turnpike in Alexandria (corner of Braddock Road).

Any recommendations? I love Patel Bros in Rockville but that's just too far.