I live in Penzance, Cornwall (GB), and we're part of Transition Penwith, which is our local area....it's too big. Well, in my opinion it is. I love the idea of Transition towns, the idea of working towards something (rather than away from) is a great one, but the area needs to be small enough that the individual feels she/ he can really make a difference.
Most people have never heard of Transition Penwith, I have a friend who's a part of it but he's frustrated because it seems that it's all talk and very little action.
The Permaculture Magazine has been following this movement closely, and gives very good explanations about what it's all about. And to add to Wikipedia, try this site -
Transition Culture