D.B.
Check with your school's art department - a lot of times that heavy material can be used for projects. Teachers are always struggling with too many kids and too small a budget.
Check your local prisons - they often have libraries with few resources, and may have files of prisoner job training info they need to file, and they are never on anyone's radar.
Freecycle - there may be a chapter near you. You'd be astounded at the things people want and trade. You have to give something away first, but thereafter you can be eligible to accept free stuff. It's a fantastic way to keep things out of the landfills! Go to Freecycle.org and see what's near you. You can arrange for people to pick up at your curb or garage, and you don't even have to be home.