For me I tuck it into my backpack. I have a standard (non photo) backpack, so it loads from the top. I'm fairly good at quickly tucking things into it and zipping it up. It's not entirely waterproof, but it's reasonably resistant, enough for Splash Mountain. I wouldn't count on it to keep my camera dry in Kali though. For heavy rain the backpack has a rain fly which experience tells me I can rely on, in RAIN.. but in Kali the water comes from too many angles, I can't be certain that the fly would fully protect it.
I think the plastic bag may be an even better solution in some ways, I actually have ziplock bags big enough to close around my camera as long as I don't have a long lens on it. It would be faster to slip a camera inside a bag. But with it in my backpack I can just leave it there when I get off the ride, I have less things to hold and I can leave it safe and dry while my clothes and skin are drying off.
I admit I'm sorely tempted to pick up a waterproof P&S for this year.. but Olympus seems to make about the only option available and the word is the autofocus isn't too reliable, plus I'm unhappy that it uses XD instead of SD cards.
I'd really like to get a shot on Kali. I could get so many good shocked expressions if I could time the shot just right for when a wall of water is crashing down on us.
