The first ones in Illinois that come to mind are in Chicago Public Schools, Rockford, Springfield, Peoria.
To see more, with more and different options, in Illinois, go to http://www.k12tlc.net/ilgt.htm and scroll down.
Consultant and Parent Affiliates Chairman, IL Association for Gifted Children
Member, IL State Board of Education Advisory Council on the Education of Gifted and Talented Children
P.S.: If you live in Illinois, go to http://www.iagcgifted.org and click on Parent Affiliates to see if any groups are near you.