we do a raffle every spring, where we go around to area businesses and ask for donations (discounts on restaurants, gift certificates... we even got a harmonica from the music store lol but just ask for anythingggg) and then we do a raffle using the prizes and sell tickets i think for like 1 dollar or 5 for an arms length and sat in our student union and went around to professors, and other greek chapters. we used it for our philanthropy, the american cancer society... the first time we did it- we got crappy prizes and didn't raise much but the last few years have been successful, so don't get discouraged
another thing we do is we sponsor the homecoming king- and we ask guys to participate (its a big deal to do so) and they go around and collect change for the american cancer society and the guy that raises the most is crowned homecoming king...
we also threw parties lol but with 6 sisters thats kind of hard to do....
good luck!!! pm me if you have questions