Skate on State has now transferred homes and names. Chicago's impressive Millennium Park now houses the McCormick-Tribune Ice Rink. Skating is free for those who have their own skates and  is only $7 for those who need to rent. There is no time limit on renting skates. From mid-November till early March the rink is open at 10am all week long. It closes at 8pm Tuesday, Wednesday, Thursday, and Saturday. The closing time extends until 10pm on Sundays, Mondays, and Fridays.
The rink is a reasonable size, and they get everyone off the ice for about 10 to 15 minutes a few times a day to touch up the ice. Watch out for out-of-control kids (and a few adults!).