our alum groups participate annually in the safeplace walk (
http://www.austin-safeplace.org/default.htm) in our city. this year we had an excellent team leader who helped us raise five times our goal, which resulted in our team being one of the top five teams participating in the walk. additionally, we had the largest team and largest day-of turnout of any greek organization participating in the walk. several members on our team also raised enough funds individually to be recoginzed as "walk-stars" at the event.
i think the key to this event being successful for us was the strong motivation and inspiration given to us by our team leader. we recieved weekly emails updating us on our team's progress, inspirational stories, and friendly encouragement, but nothing over the top.
we have been working on some more philanthropy ideas, like partnering with a local high school for a prom dress exchange and a fundraising garage sale, but those are still in progress. hopefully they'll be as successful as the walk we do each spring!