There are some great articles online about green weddings, starting with this one from the sierra club:
http://sierraclub.typepad.com/greenlife/2007/03/10_steps_to_a_g.html
I fell in love with the idea of wedding invitations that have seeds embedded that you can plant. So you take the entire invitation and stick it in the ground and it grows plants! Genius! Here’s one company I found that does seeded paper and invitations.:
http://www.greenfieldpaper.com/index.cfm