I can second Kevin Leavitt's mention of the wealth of aikido in and around DC. I cut my teeth with Takeguchi Sensei at Capital Aikikai, and there are several other good dojos in the area.
On a side thread, I teach on an army base (Ft. Detrick, Frederick, MD), but get very few military in the class. I've had a few MPs, but that's about it. My theory is that 1) the class is too late in the evening, we start at 7:30 pm, or 1930 as they like to say, and most of the military folks have been up since 0-dark-30. and 2) aikido may be perceived to be too docile a martial art for many hard core military types. Anyone else had a similar experience?