If you're looking for wrecks to dive in the Chicago area, get yourself a copy of Cris Kohl's Great Lakes Diving Guide (I think the his website is www.seawolfcommunications.com) and enjoy. The further north you go, the better condition the wrecks are in. Of course, they're in better condition because they're in deeper water and tougher dives, too.
If you're looking for charters to take you to the wrecks, your options include...
Pastrick Marina, Gary
Burnham Harbor, Chicago
Waukegan
Milwaukee River, Milwaukee
If I missed anybody, I'm sure I'll hear about it.
If you're looking for charters to take you to the wrecks, your options include...
Pastrick Marina, Gary
N'Pursuit Adventures: http://www.npursuitcharters.com/index.html
Burnham Harbor, Chicago
Dive Chicago: http://www.divechicago.com/
Waukegan
Enterprise Marine: http://www.captaindales.com/enterprise_marine.htm
Milwaukee River, Milwaukee
If I missed anybody, I'm sure I'll hear about it.