Speaker for Earth Day or organic foods forum

Hey - I'm writing on behalf of the Bryn Mawr College Greens - we're looking
for a speaker to bring to campus to celebrate Earth Day, and/or to
participate in a forum being organized on organic foods and out dining
halls, etc.

Are there any people out there interested, willing, or who know someone who
would be perfect? Someone local to the PA/Philly area might be best,but
good ideas are appreciated, too!