Crystal Ridge (http://www.crystalridge.qpg.com/) is about 70 minutes from O'Hare. The site is well suited for beginners and kids and yet has enough difficult trails to challenge experienced skiers. Day-time sessions are open from 10:00 am to 4:30 pm. The address is:
Crystal Ridge Ski Resort
7900 West Crystal Ridge Drive
Franklin, WI 53132
(414)529-7676