If you're interested in Guerilla Gardening and start-up Community Gardening efforts, here's a group for you. 

I, Justin Thakar, will be cataloging, here and on my TransitionPGH.org blog, what I will have learned and a list of resources I will have compiled.

I've already been talking to my apartment neighbors about doing some collaborative container/balcony gardening, splitting the produce and such--and I'll be putting up invites on everyone's doors to see if they're interested.That's material no.1 you'll see here: examples of how I will have been trying to get the community around me involved in learning intensive growing skills. 

And I still intend to get in touch with Chris Condello, of the Whitney Avenue Urban Farm about figuring out how to effectively Guerilla Garden while involving the community around Pittsburgh, and learn from his successes, and aside from that there's plenty of resources (as you might see from the picture above) and online: 

http://www.guerrillagardening.org/

http://transitionpgh.org/photo/albums/whitney-avenue-urban-farm

If you have knowledge and resources to share, certainly do so in the comments section.