I would really be interested in this too...we can get good hotel deals near O'Hare via Hotwire and have found a great offsite parking lot, but I don't know what we're going to do at Midway for our March and April trips.
Barb
Visit the Platinum Castaway Club at: www.castawayclub.com
Here's a link the the airports from the Midway page. It looks like a couple offer parking and shuttles but they don't list any specifics. Might be worth a phone call!