Middle Eastern Markets
In Rockville, about 1/4 mile north of the Twinbrook Metro station is Yekta Market. It's hidden behind the On The Border (next to the infamous Sichuan restaurant Joe's Noodle.) Very nice Persian market with plentiful produce and spices, and also attached to a very good kabob house.
If you need even more spices, another half mile up Rockville Pike is Penzey's spices.
Yekta Deli Imported Grocery
1488 Rockville Pike, Rockville, MD 20852
Metro is not your friend, unfortunately.
Mediterranean Bakery in Alexandria is the probably the biggest and has lots of spices. It is not the best of the best. King Street Metro is a good 5-10 minute cab ride away.
Mediterranean Gourmet Market on Franconia Road near Springfield Mall is smaller but better. Outstanding menu and much better sfeeha. About a 5-minute cab ride from the Springfield Metro.
Lebanese Butcher in Annadale is just about everyone's favorite around this Board. West Falls Church Metro is a 5 minute cab ride away.
Lebanese Taverna market in Arlington is also loaded with selections. It's about 5 minutes by cab from the Ballston Metro.
There is a middle eastern market on University a couple of blocks north of the Wheaton Metro. It's a small middle eastern speciality shop, but I cannot remember the name right now! But it is on University just east of Viers Mill in the heart of Wheaton. They have a great selection of spices.
Someone on chound recommended it to me when I was looking for preserved lemons. Maybe google to get the name? Good luck!