What about any local church groups in the area. They may be willing to either except donations or perhaps host a sale of your fabrics. I can't believe anyone would turn down 100% cotton fabric. (Although, I know some can be picky about fabric.)
Craig"s list is also a great idea for fabric. Just be careful, don't allow any strangers in your home and if you have a pick up from your home, have someone else there with you. My daughter does a lot of buying of baby items online, also selling, but never meets at her home. Usually a Wal-mart parking lot during PEAK shopping times. (But, she's usually meeting military wifes.) She lives in a military town and has a husband in the military.
Also, is there a Fashion design school in the area or a Performing Arts School? Maybe they would take some donations. Especially if there is fabric that is of a mixed blend.