Climb the Art Museum steps and GO INSIDE. It's a beautiful museum with a ton of famous art from many different eras. The Barnes has a ton of incredible art, too, mostly impressionism.
Most of the history stuff is probably obvious, but I took a tour into the tower of city hall that was pretty interesting. I don't know if they still do it.
Get a cheesesteak, sure, but get a roast pork sandwich. If you go to Reading Terminal Market, get it from Dinic's. While you're there, get a Beiler's doughnut.
Most of what I like is not touristy stuff, I guess. There are some really nice parks and neighborhoods I like to hang out in. I can recommend coffee shops.