East coast and Chicago? I would be checking AA
, US to fly an american carrier. Is sounds like you coming to the states and then hopping around the east coast. Is that right? What's your Europe departure point?
Fares should be available now for the summer, but airlines haven't announced most service enhancements yet for summer 08. I would be looking to buy sometime in January '08. There are some neat sites that track fare levels and tell you when the best time to buy would be. Pull up a search engine and get on these. Farecast.com is one example.
Best of luck and enjoy your trip!
...carelessness and overconfidence are usually far more dangerous than deliberately accepted risks. - Wilbur Wright