Want to recommend a site listed in the March 2002 issue of
Smithsonian Magazine - the one with the cover story on
recreational tree climbing. This
http://www.dancingwithtrees.com site is about Genevieve
Summers and her guided climbs, expeditions, and advanced
training courses. She does brief intro climbs for groups
too. Also offers overnight camping in the trees. Site also
has quotations about trees and lots of good links.