Mashable recently wrote a story about CauseWorld, the hit iphone/android app that lets people "check in" at a store or location and 
then earn "karma points" which convert to real money (about $0.01/karma) by sponsor-companies and can be donated to real charities or funds by just clicking a button on the phone.
The "check-in" craze, pushed forward by Foursquare and others like Loopt, GoWalla and now Facebook Places, is where users who are in a certain place "check-in" to declare where they are and potentially see others around them.
Foursquare pioneered the game-mentality taking the meme by storm 
where you get "badges" and other special status for doing certain activities. For example, if you check-in to a location more than anyone, you become that location’s "mayor."
Merchants caught on quickly, realizing that this amounted to free, social advertising of their establishment and encourage check-ins with free drinks or a side-entree from their favorite restaurant for checking in, or a "always free drinks" for the current "mayor".
Moving this to the charity world is an interesting dynamic. I am still studying, but it appears that CauseWorld and other upcoming charity check-in apps can bring real money to needy causes while letting users have a good time along the way.
Also from Mashable about online giving:
Robert Merrill 