Just off the top of my head here are some properties and approximate walking distances, give or take a city block, from the IC in Chicago:

Chicago Marriott Downtown (across the steet)
Sheraton Chicago Hotel and Towers (3 - 4 blocks)
Hilton Garden Inn on Grand Avenue (3 - 4 blocks)
Homewood Suites on Grand Avenue (2 - 3 blocks)
W Chicago Lakeshore (6 - 7 blocks)
Westin River North (4 - 5 blocks)
Westin Michigan Avenue (5 - 6 blocks)

I believe there are also a few Hyatt properties a Courtyard by Marriott and a Hampton Inn all within a few blocks as well.

As for transportation, I would go for a cab or Airport Express from O'Hare as parking in the vicinity of Michigan Avenue is at least $20 per day.