Hi everyone,
The Smithsonian's Archives of American Gardens is seeking a Wikipedian who'd like to lead the creation of an article about them. This article can be as complex as you desire (please not just a stub! LOL). Please ping me off list if you'd like to take the lead on this and I'll put you in touch with them. (And no, you don't have to be a horticulturalist to do the job!)
http://gardens.si.edu/horticulture/res_ed/AAG/home.htm
You don't have to live in Washington, DC, so don't worry about that. It'd be a cool opportunity!
Thanks!
-Sarah