This self-described “journal of the politics of driving” is a tremendous resource. Photo Enforcement is the author’s primary focus.
This site discusses red-light cameras, including their common errors. It’s great for anyone fighting a camera ticket, especially in California.
This site features a user-maintained list of red-light cameras and photo radar locations throughout the United States. You can even add to the list.
POI Factory has a free database of camera locations for GPS users. The data is cooperatively maintained and free to active participants on the site.