Japan
Radiation contour map by Yukio Hayakawa (8th Edition, Feb 2013) [GoogleMap] [Download Map]
Global
Fukushima Radiation – Comparison Map
The Guardian: Nuclear power stations and reactors operational around the world: listed and mapped
Infographic: Map Shows Nuclear Reactors in Quake Zones
Nuclear development, Testing and Dump sites in United States
An interactive map with the location of every reactor in the world
Worldwide map of nuclear power stations and earthquake zones
Comparative reference:
文科省NAVER: Radiation map by Ministry of Education, Culture, Sports, Science and Technology, Japan