We do have an active DIY scene here in Chicago, but online organization is admittedly not the best. Things are changing though and we're making progress, but there is typically somewhere to go every week that is all-ages and/or DIY. Don't be afraid to sign up on CPP, we're a friendly lot and I've met a good collection of folks specifically because of that site, young and old. And feel free to drop a PM if you have any specific questions...
Best sources of info, focused more on the punk/hardcore side of things:
Chicago Punk Pix shows page - Should be noted that I'm a moderator there. We just implemented a calendar function this week (have to be registered to use it) and plan to keep it as up to date as possible. Lots of listings for DIY and all-ages shows.
Chicago Hardcore shows board - definitely a younger crowd here and a lot of under ages.
Southkore Records shows page
Specific DIY venues:
* La Casa Maldita
* People's Projects
* The Butcher Shop
* Lucky Gator Loft
* Ranchos Huevos
* Sludges
Venues that play a good deal of all-ages shows:
* Beat Kitchen
* Champs Rock Room
* Reggies
* Stage 83