Quoted from jahbarron:
Logan Arcade (pinball/arcade/air conditioning)
Hot G Dog (hot dogs; basically the grunt behind the famous Hot Doug's)
Foster Avenue Beach (beautiful Lake Michigan)
Simons or Green Mill (bar/air conditioning)
Music Box (movies)
I like this list a bit better as I usually steer people away from the tourist traps. There are always music fests going on from now thru Septmeber if you like live music. I don’t like deep dish pizza (thin crust tavern style is what the locals all eat). I will say that all of our museums are world class and never get old to me and I’ve been to them all a million times (Art Institute included). It’s a tough city to beat in the summertime.