UA: DEN-ORD $116 a.i. r.t. Mar 3-5
Just booked this, as I haven't been to Chicago in a while, and this is as good as it gets, especially for leaving Friday evening and returning Sunday night. The fares are even cheaper ($14-$28 less for r.t.) if willing to leave on Wednesday and return on Tuesday.
$0.065/mi, which is the best I have ever purchased for DEN-ORD.