I'll be visiting the area in Oct; at the FSGW gathering Oct 19 to 22 and then playing at Southern Maryland Traditional Music and Dance Coffee House located at the Sotterly Plantation (301-862-1928 for concert info) on Thu Oct 18.

You will want to check out Mudcatter, Seamus Kennedy who performs in the DC area pretty regularly. His calendar is here.

As Rita says above, as a Mudcatter and DC area music lover, you will also want to check out the Folk Society of Greater Washington (FSGW) and the FSGW Getaway that is happening in mid-Oct. There will be many Mudcatters there.