Phone cards (International) - Where do you find these, if I may ask - or can you simply donate and they will be purchased by the people at the site
Just about the cheapest and best deal around are the 500 minute AT&T cards from the Army and Air Force Exchange Service web site. The specific URL for their program is:
https://thor.aafes.com/scs/default.aspx
You don't need to be an authorized user to purchase them, and they will send the card you purchase to anywhere you want. They'll send overseas to an APO/FPO, or you can enter the address for organizations such as Proud Patriots (see above).