Yeah, we do most of our communication on the ChicagoParkour forums, I still check these quite often though, I think at least one or two others do as well.
I believe there are a few people in Naperville, and I know there are a good number in Plainfield/Aurora as well. I'm in Schaumburg myself, but go to a gym in Oswego (Premier), almost every Sunday night. As long as we have 5+ people, it's only $10 for 2 hours or more of training there, as well as an annual $30 if you plan on going more than once.