We have Teeter Totter with Alpha Gamma Rho. We have (and I have NO idea where they came from
) 2 gigantic see-saws and the rules are there has to be one boy and one girl on each side at all times. This is a 12 hour event! We made money by each member of both orgs collecting at least a $20 donation. The money is split between both groups philanthropies. But it is tons of fun!!! We sometimes do this in the Wal-Mart parking lot to get donations, too.
We have a Christmas party with Pi Kappa Alpha for underpriviledged children. We get a list of names from Human Services, I think- but each child is "adopted" by several members- we buy them gifts, then have a Christmas party at the Pike house, complete with caroling and Santa. It's always a lot of fun.
I just think the most important thing is to keep it fun and laid back- and remember why you're doing whatever event you're doing.