Freecycle & Craigslist:
These two have been around for decades, and both have a feast-or-famine reputation: You’re either lucky enough to live where there’s a great group offering great things, or you live in a place where people try to unload some pretty awful stuff. (Fun fact: A guy in Fairbanks, Alaska, advertised free dog poop — “You shovel, you haul.”)
Back in my starving-midlife-student years, I scored some free grub from Freecycle and Craigslist. You might luck out, too.