Originally Posted by Nanook
Whether it's paper money or coins, you can mail it to Change for Good. The coin envelopes are usually given out to passengers going to the US from many foreign countries. They FAs collect them and they go to help Unicef. Here is a link:
http://www.unicefusa.org/site/pp.asp...RI8O0H&b=25945
Excellent ^ ^
I usually try and either spend all I can before I leave, or just plan on keeping a souvenier.