I've recently started to consider obtaining some more formal training in gardening. Perhaps you have too?
Here are the educational opportunities available in the DC/VA area:
Free or Cheap:
Merrifield Garden Center Seminars
US Botanic Gardens
A Bit More Pricey:
Northern VA Community College
Grad School (formerly USDA Grad School)
Most Expensive (Also Requires Commitment to Degree Completion):
George Washington University Professional School
I've personally gone to one of the Merrifield Garden Center seminars (on seed starting, you might recall). I enjoyed it and felt it was informative. Plus, it was free! So, I'd start there if you're interested.