If there's only a slight chance of rain I bring a cheapy rain poncho but the rest of my family brings nothing -- they don't mind getting wet in their park clothing (I do). If it's going to rain all day, we bring our Disney rain ponchos. I've considered buying the lightweight rain jackets that fold up small enough to fit in a large pocket, but they're shorter than the rain ponchos and I prefer the longer coverage the ponchos offer.