These shops are probably both somewhere in this thread, but are worth mentioning again because I have dealt with them recently:

A few Chicago bike shops worth visiting:

1. Cycle Smithy: http://www.cyclesmithy.com/ If you are a bike geek, check out this shop. Stop by, take a look at the ceiling. The store has a bike museum hanging from the rafters! They also carry a stock of track bikes, not a fantastic selection, but the hanging bikes make a visit to this shop worthwhile.
2. Yojimbo's Garabge: http://yojimbosgarage.com/ Marcus runs a great shop, track friendly, tons of goodies in stock, and reasonable prices.