Usually searching your city/metro name and wood chips will do it.
In my area someone created an app-based program called Chip Drop. Deliveries are free and you have the option to specify what you don't want (large piece, wood of particular species). Also you have the option to pay if you want to- if you find something like this, PAY. For <$5 I get cubic yards of what I want, instead of what's left over after someone else gets the goods.
Unless you're not talking about woodchips? There's often lumber of some kind available on Craigslist under the free section, in my
experience. That's rarely delivered, though.