long exposure - Are there any resources or websites for finding areas which have low levels of light pollution at night?

Are there any websites which map light pollution levels so I know where to go for decent long exposure night shots? Or general resources for that matter?

Answer

I would start at the International Dark Sky Association. They have detailed maps for North America and also a link to the Blue Marble Navigator for the rest of the world. Although a little older, I find these maps of North America more readable.