The amount of haze, combined with the height of the sun in the sky, determines whether I'll use straight Sunny 16 or more usually Sunny 11 around here. But for beach or snow shots, where the ground bounces back a lot of light, I usually go for the full Sunny 16. And of course I adjust for different densities of cloud, as has been described earlier in the thread. In the golden hour I tend to work off f/8, but really it's about using experience to judge the particular conditions by eye.
Around here there's usually some cloud, and I prefer to expose so that the brightest parts of any cloud will be just below clipping (assuming that the sun isn't directly in the frame). That quite often means that there's some shadow recovery needed on the ground, but that's easy with digital.
For people who want to get into Sunny 16, I'd suggest doing a series of test shots on a sunlit day, with some clouds with bright highlights but not with the sun directly in the frame. Find the exposure that captures the brightest parts of the clouds at just below clipping, and from now on you can use that as your standard "Sunny 16". My normal Dartmoor exposure is f/11 at 1/125 at ISO100. Switching to f/16 at 1/125 at ISO100 in sunlit snow, and of course opening up as needed when there's cloud. It's not
strictly Sunny 16, but it works for me.
Edit: The height of the sun in the sky is relevant based on the time of day, not time of year. I use the same exposure in direct noon sunlight on 21st December as I do on 21st June. But at any time of the year, as the sun drops towards the horizon and the colour of the light visibly changes, you need to adjust exposure. In the summer there are more hours where you can go full Sunny 16, and the winter there are more hours of the day where you need to open the lens up a bit. The colour of the light is the best guide.