AES in Milwaukee is a fun place to go if you're got $ in your pocket and know exactly what you want. As far as a place to browse? Nope. Not like it used to be. They usually have a few shelves of used gear, but all over priced.
Geezer story: Ahh, now 'back in the day', when Heathkit was right next door, THEN you could blow a few hours. Start at Amateur, poke around, then go to Heathkit and play with their SB104 station they had up on the air. When they moved out, Radio Recyclers (used/consignment) moved in and again, you could blow an hour in here. He had gear and he had bins upon bins of parts. You could spend $1,000 or as little as $0.25 and come out with a smile on your face. :^)
Thinking more: I've never been there, but I hear that CHester's Electronics in Kenosha, WI is a great place to go and browse. I've driven by and it's quite large.