Hey, I just had my interview this past week.
O'Hare and Midway are probably your options if I remember correctly.
O'Hare was actually much farther away from ICO (cost us around $45
to get there from the Airport, and pretty much the same to get back).
I have heard that Midway is closer to ICO, so if your looking to save a few bucks, Midway might be the way to go.
Hope that helps.