[cuteASAbug]

You can do a penny war, or for a more "fun" take on it, you can do something similar to Cornell's Best Jugs on Campus:
One of the fraternities sponsors it and gets giant water jugs (like from a water cooler) for all of the sororities. 1 jug/sorority. Each sorority decorates the jug however they want to and then for a few day- a week the jugs are displayed in a prominent and secure location around campus. People can come and vote for whichever jug they think is the best by putting money in it. The sorority that has the most money in theirs at the end of the week is the winner. Half of the total money raised goes to the sponsoring fraternity's philanthropy, and the other half goes to the winning sorority's philanthropy.