I've been kicking around this idea for a while. A few forums I frequent do this, and you end up getting some neat stuff.
Basically what happens is a bunch of folks sign up.. a dollar amount is set (usually $10-25ish), and your name is randomily given to someone else. Gifts are mailed and everyone feels good.
The problem lays in that some people sign up and don't bother sending a gift (due to lazyness usually, not intended), but for the most part it works out well.