I've heard that there's a big demand for bras in some African countries, because there currently isn't much manufacturing of bras available. So you donate them to a local charity?
I love this idea! Its perfect cause most of the bras I have are in good condition.
I had this same problem. Old bras that I didn't know what to do with... So I donated them here: http://brarecycling.com/ Their website says, "Our bras are distributed around the world through exporters and Bra Recycling Ambassadors to deserving women and girls in transition." I think there are other companies that do the same thing.