If you're looking for somewhere to rest your head before embarking on your road trip then you could do far worse than The Inn at Lincoln Park. It's a cosy hotel just a short bus/taxi ride from the center of Chicago and is a great location for a spot of sightseeing.
The front desk is very nice - fresh fruit, cookies, coffee and tea available in the lobby 24/7 - and the staff are welcoming. The breakfast is a self-serve buffet with a more than adequate selection (eggs/bacon, muffins/waffles, cereal etc...). I definitely felt as though I was hitting the road having been well fed!
The rooms aren't huge and the decor is a little dated but the rates are competitive and a good deal for the location. Situated in a trendy neighborhood, it has the feel of a European hotel and not your usual cookie-cutter American chain.
As an aside, if you get the chance, pop across the road and have a bite to eat at Red Hen Bread - they serve a fantastic selection of cakes and sandwiches. My wife and I had a great lunch there while we planned the next day's travel. My stay here was an excellent start to our Route 66 vacation.