I'm taking a vacation to Milwaukee, what should I do?

I'm going to be in town from Wednesday (27) night until Sunday (1) morning. So far I'm going to check out Summerfest with one of my friends, but she'll have to work during the days so I'll need something else to do. I know you're pretty famous for beer; are there any breweries that are must sees or that give awesome tours? Are there any breakfast places or diners that I need to check out? Thanks!