I work in a rehab center.
Do you know anyone who works in a nursing home or hospital? They throw out bags of stuff every month! Sheets, blankets, pillow cases, but my favorite is the bath blankets. They take dye so well! And can be cut and unhemmed for costumes and don't run. I've made lots of things out of the sheets and bath blankets that I've gotten from work.
Speak with the head of housekeeping at a local hospital or nursing home and ask them if you can have the linen's they throw out. They can't keep stained (a lot of treatment meds stain and even the super hot industrial washer's they use can't get it out) or torn items so it goes to the trash!