What a great way to make use of some spare money that would otherwise get wasted. 
springwise:

From unused subway fares, a monthly donation to charity
Every year, some USD 52 million is lost by users of New York City’s MetroCard payment system when they replace old cards that still have a small amount of value remaining. Aiming to put that leftover money to better use, MetroChange is a new system designed to capture that last bit of change on old cards and donate it to charity instead. READ MORE…