Here are a bunch of air cannon links culled from the MOM list.
http://ourworld.compuserve.com/homepages/p_s_parsons/se2000.htmlhttp://www.xinventions.com/main/spud/home.htmhttp://ourworld.compuserve.com/homepages/p_s_parsons/cost.htmhttp://www.spudtech.com/http://www.marcogliese.org/spud/index.htmlhttp://www.corin.com/bill/paintball/aircannon/