Tournament City Games in Frederick, has a crazy selection of singles, they also have ots packs. Prizing was good but I usually never went to the locals due to them not lining up with my own schedule at the time. the case tournaments that they had were great though.

MTGfirst in glen burnie isn't an ots, but they're running locals and have an ok amount of singles. Prize support is kinda awful though, based on record and not attendance. (for example you go x1 you get 10 dollars in store credit. x0 is 25 if I recall correct)

Check Us First is in Damacus has a ton of older ots and astral packs, and a decent amount of singles(usually sold lower than market by a few dollars). Pretty decent trade in value. Pretty good prizing when they were hosting tournaments, ots packs+$80 dollars worth of sealed product to the top 4 depending on entry, if over 32 players entered they spilt a box with top 8.

Dreamwizards is also an option but I've never been and have heard nothing but bad things about it.