Why not have the presenters provide seed packets for sale for those tomatoes they are displaying at the event? I know there were some (Cossack Pineapple, Flat Head Monster, Black Cherry, etc.0 that I would have liked to have purchased once I tasted how unusual they were.
My blog post for Tomatopalooza 2012
http://eptemplate.wordpress.com/2012/07/30/tomatopalooza-2012/
Flickr Photo Set for Tomatopalooza 2012
http://www.flickr.com/photos/billg2/sets/72157630820315046/