There is a new gluten free vendor at the Middletown Farmer's Market (off of Rt 40A, between Frederick and Boonsboro). Casey Sisters Sweets https://www.facebook.com/CaseySistersSweets makes only gluten free breads, cakes, cookies, cupcakes, etc. The selection changes each week and they are available for custom work.
The market's hours are Thursdays, from 3 to 6 pm. http://www.local-farmers-markets.com/market/2262/middletown/middletown-farmers-market
Disclosure: I know one of the Casey sisters through L'Academie de Cuisine. She is completing her externship at Tabard and training under Pastry Chef Huw Griffiths. I have personally tried and enjoyed her gluten free pastries. They taste remarkably close to conventional wheat products.