Wolf Trap's bonsai stock is a little on the expensive side and not that great. They get their bonsai from Meehan's Miniatures in Md.
Gardens Unlimited is owned by Todd Stewart and Bob Chilton.
A recent article from the Richmond Times Dispatch:
http://www.inrich.com/cva/ric/searc...12-01-0001.html
Don't miss the slide show with the article.
It's arguably the best bonsai nursery in the area. I've known them for 12 years or so and have watched them develop their nursery from a backyard operation to a much bigger nursery in that time.
Definitely look into a local club. You will find the quality of stock that becomes available through a club pretty astounding--several notches above what is available in any of the local landscape nurseries around--and MUCH less expensive. Clubs have auctions every spring and you can also find members selling off trees to make room for new additions.