Another recommendation for the Goethe Institut. It was more expensive than the Graduate School USDA, which is where most people in DC go. However, the instructors were native speakers and motivated to teach. More than that, the students were motivated to learn, and not because of a paper job qualification or university breadth requirement-- rather, their fiancé was from Leipzig, or they had been appointed head of their company's Vienna office. Plus it was less expensive and more social than tutoring, and we got to see our teacher's bemusement if anyone used an expression that turned out to be Swiss.

Also for those who like irony, it was the most prominent cultural institution in Washington's "Chinatown."