Some of the things local schools that do that are very successful:
An auction night - local businesses can donate products, parents can donate services depending on various skills. For instance, someone offered to cook a romantic meal for two, another person offered to draw a portrait etc, then people bid on it.
Garage Sale - everyone brings all there old stuff, advertise it in the local paper/radio etc, then sell it all off in the school hall. Needs a lot of parent help but it can raise a lot if combines with sausage sizzle, bake a cake, face painting by children etc.
I'll keep thinking ....
Cheers
Tia