DOE Nevada Operations Office for the excellent photos and a lots of info.
VCE - Visual Concept Entertainment for the movie Trinity and beyond - The atomic bomb movie, this is an excellent collection of many nuclear explosion footages, most of those were classified for a long time, now remastered and improved, they are available. Film includes lots of nuclear test scenes, technical information, Edward Teller and Frank Shelton interviews and comments, describing different weapons, historical events, etc.
Carey Sublette- For his Nuclear Weapons Frequently Asked Questions, created and maintained by him.
Los Alamos National Laboratory - For their help in filling the gaps in history and solving picture puzzles :)