Arlington is my spot to meet women, specifically in the 22-27 range. Clarendon especially is full of young professionals.
In DC you get more of a mixed crowd. Dupont Circle and Glover Park are areas I frequent pretty often. If you are into college age chicks Glover Park, U Street Corridor, and Adams Morgan seem like the places to go. I always meet 19 year olds out in those areas, especially at McFadden's.
I'd be down to get out there with anyone in the DC area looking to hone skills.