I will catch up! I WILL!
Some years back I worked with a group that ran a small gaming convention with the proceeds going to a children's charity. That was pretty awesome.
While it might not totally qualify for what the question is asking, I'd have to say my favorite use of RPGs in aid of the community is the programs we've run at the learning and tutoring center where I work on Sundays.
Located in a middle class, predominately Chinese neighborhood of Bay Ridge, Brooklyn, my ex-wife started a center that provides homework help during the week, and additional education on the weekends. She hired me on some five years ago, or so to facilitate a program using role-playing games to teach the kids English reading, writing, and speaking.
Over the years, the program has greatly assisted our students, many of who live in households where English is a second language, Listening to, talking about, and writing stories with their characters, and the worlds those character inhabit, all in English, has improved the creative, and cognitive skills of a large number of kids.
I'm very proud to have been part of this idea, and that I can continue to do so.