The absurdly talented and all-around great guy Rob Hinkal and his great band iliAIMY, who you MUST see. Rob hosts several great open around the area and virtually. Check it out.
Rob Hinkal and David Eisner with help from Juels and Clif host a great open mic in Takoma Park each Tuesday. This it not a loud bar where people only barely pay attention. This place is a listening room with great acoustics and a lot of local talent to see. Music starts at 7pm.
Jon Watkins hosts a great open mic on the 1st Wednesday of the month from 6pm to about 8:30. Great local songwriters and microbrews, and the vats are right there with you. A big space with a booming sound. Bring your own food. Children are welcome.
The legendary Madams Organ hosts an open mic on the second floor every Wednesday night. Music starts at 9pm and goes until whenever. Always great local talent.

MacKenzie's in Fairfax, VA hosts an open mic every Wednesday from 7:30 to 10pm. Good food and drink there too.