If you're ever in the northwest Chicago suburbs, you must visit Emmett's Tavern and Brewing Company in West Dundee. I used to live a few blocks from there (so it's my sentimental favorite), but I can honestly say that they have some of the best beer I've ever had, especially the Victory Pale Ale. The food is excellent as well, and it's kind of a nice upscale place to go for dinner with friends.
On a less upscale note, I try to visit Bent River Brewing whenever I'm in the Quad Cities (Moline, IL). It's almost the polar opposite of Emmett's atmosphere-wise, but those hippies make some good beer! Try the Dry-hopped Pale if you're a hophead, or have a Jalopahop (half Jalapeno beer, half dry-hopped pale).