Clearview Research is a Chicago based market research company. They hold focus groups in the Rosemont area, just north of O’hare. I have done several groups with them and have found them very easy to work with. They also have free parking (a big plus!) in a lot behind their facility and are just off of the expressway. They will typically contact you by email, asking you to call if you are interested, available, and think that you qualify for the study mentioned.
Although the main facility is in Rosemont, I have also been contacted by them for in-home studies and studies downtown, so it might be worth signing up even if Rosemont is not in your general vicinity. Read the list of included zip codes to make sure you are within their research area.
If you want information about additional market research companies, you can read about them here or here.