So far, my husband and I haven't done this yet with our own kids. This is our first Chirstmas as college graduates with a well paying job, unfortunately for us, we're still the proud owners of two houses (still counting down until the 18th when our Provo home is supposed to close), so the 12 Days of Christmas might have to wait until next year.
Interesting Tid bit: After attending a Christmas event, I learned an interesting fact: apparently, all these years, my family has done the 12 days of Christmas all wrong--according to Catholic tradition, the 12 days of Christmas start December 25th--who knew!
If you shy away from door-bell-ditching, I also love Toys for Tots. Noah and I have tried to do this the last few years because you don't need much money at all to get a small toy for a child.
My very favorite foundation though is Heifer International. We found out about this organization through my Aunt Lisa. Instead of giving toys that will break or be forgotten, you give a family the gift of self reliance. By donating anything from livestock to honey bees (donations start at about $10 and go up to $5000), families can start having a source of income and put food on their table. My favorite part about this organization though is their "pass it on approach," where the recipient of your gift agrees to donate the offspring of it to other families in need. You can read about it here.