From now through September 30, 2010, if you turn in $40 worth of coins at a CoinStar machine, you'll get $10 iTunes gift certificate.
CoinStar machines do deduct a fee, about 10% from you coin total, but since the fee on $40 would be about $4.00, and the gift certificate's worth $10, you'll still be $6.00 ahead.
You have to use the gift certificate before October 31, 2010.
For all the fine print on this offer, and to find a CoinStar machine near you, click here.
Thanks to Bargain Babe for this tip.