Keep the Change"(tm) program. The concept's illustrated in the picture to the right, basically rounding up any charged amount to the nearest dollar and putting the rounded up amount into one's savings account.
The creative folks at IDEO were the ones to propose the Keep the Change program to Bank of America and it was launched back in October 2005 as a way to stimulate folks to create new accounts at BofA. (evidently it did quite well)
From what I can tell, BofA's success hasn't gone unpunished. A group called Every Penny Counts® is suing both Bank of America and VISA for infringing their 1993 "Rounder Patent" issued in August 2000.
I haven't yet figured out where the legal proceedings have gotten, but I'd offer this suggestion to all involved: open the patent so anyone can use it philanthropically. (Didn't Eddie Murphy have a movie wherein he stole the fractions of a cent rounded off of trades and make a mint doing so? anyone?)
So, I wonder how difficult/costly it would be to do something similar to Keep the Change, only direct the "rounded up" amount to one's charity of choice instead of one's own savings account. Conceptually, it seems like this could piggy-back off an existing payments program, and the brand halo could be enormous.
I've even got a name for the program: "Donate the Change."
Lest you fear, I won't be claiming any legal rights to this concept. Go ahead, make it happen. We'll all be better for it.