Well, the main problem I have seen is having everyone bringing the same thing or type of thing. When everyone brings chips or brings sweets, it just doesn't work right. BYOB, but either do a collection for meat or have everyone bring their own too... plus a dish to pass (nothing too huge or we'll be able to feed the whole county!) Have people sign up dishes, and just see if we get too overloaded on something.
If I'm in town that weekend (there's some stuff going on where I don't know my schedule yet), I'd do a side of some sort like beans or a pasta salad or something... I could bake a cake too...