I backpack with a Canon 5d and have always kept the camera around my neck and my arm, which allows the camera to hang at my side. I also keep a lens hood on it to prevent it from being banged around too much. If I get in situations where the camera would be swinging around too much, I can buckle the camera under my chest strap.

My camera is also pretty water resistant so haven't had any issues with the elements. You can buy rain sleeves for your camera to be on the safe side.
_________________________
http://backpackingparadise.com