Places to Learn the Japanese Language

Japanese Language Schools and Programs in the Washington, DC Area (pdf)
Baltimore Academy of Languages
Diplomatic Language Services LLC offers language training.
The USDA graduate school has a decent range of evening classes in Japanese.
Inlingua offers private language classes at locations in Arlington and Odenton.
International Center for Language Studies Inc. offers private foreign language classes.
The Japan-American Society's Japanese Language School offers small group classes.
JHU School of Advanced International Studies has an intensive weekday evening summer language program that emphasizes "socio-political and business usage of the Japanese language."

Community Colleges

Anne Arundel County Community College Courses (they seem to have for-credit classes in Japanese but no non-credit ones)
Montgomery County Community College has a beginning for-credit Japanese class
Howard County Community College has a Beginning Japanese class that's offered every semester. No more advanced class either in continuing education or non-credit schedules.

American University's Department of Language and Foreign Studies offers for-credit classes, mainly in the morning.
George Washington University also offers for-credit classes.
Same thing for Georgetown University.
The University of Maryland has a Japanese program.