I normally just throw my old bras away (too scruffy for the charity shop). However, I was in my local Bravissimo store this week and noticed that they are doing a 'donate your old bra to charity' bin in there.
What a great idea - the bras are recycled and used in 3rd world countries for women who cant afford bras.
(Reminds me of a market stall I saw in Morocco last year which was full of old manky bras, as well as old tights!!)
Anyway, Bravissimo here I come. This campaign isn't covered on their website or publicised in any way - I just saw the bin in the corner of their store.