I'm flying to Champaign from Indianapolis actually, with a stop in Chicago. I'm visiting Indiana-Bloomington before Illinois. (Bloomington, IN hasn't an airport.)
It would seem I should be driving between some of these places, but, believe it or not, 3 one-way flights (BWI to Indy, with a stop in St. Louis; Indy to Champaign, with a stop in Chicago, and Champaign to BWI, with a stop in Chicago) was really cheap, all without the hastle of renting a car and driving long ways between.
Bloomington does have a small airport, but not many people fly into it. Good luck and if you have any Bloomington questions, drop me a line.