Well, I know that Southwest Airlines flies out of Chicago. Here in Austin, SWA is our cheapest carrier. However, I bet you have LOTS of charter airlines available to you in Chicago! Here are some other web sites that I have used:
And as far as hotel rates, I usually find that going to the actual hotel website is the cheapest (Treasure Island, Mirage, Paris, Venetian, etc)
Good luck - let us know where you stay. We are going in June.