An online application using Google Maps to show the radii of certain effects and damage due to a nuclear blast. You can pick a location (such as your hometown) and enter the size of the nuclear weapon. The site has various preset sizes based on historical weapons, or you can enter your own amount. It doesn't consider MIRVs, so you would need to do multiple maps to get an idea of the damage from the pattern of explosions from that type of warhead. The site doesn't calculate fallout patterns, unfortunately.
There is an article at the Daily Mail discussing the application and an interview with the creator, Alex Wellerstein. Says Wellerstein:
Dr Wellerstein, who is a Ph.D graduate from Harvard University, says he uses the 'Nukemap' to bring help his students understand the implications of nuclear warfare.
'I've done different types of map based teaching for the students because I've found that students don't really have a sense of how big a nuclear explosion is,' said the 30-year-old, who lives with his wife in Washington, DC.
'What I like about the map is it makes the explosions look large and impressive but it shows it isn't the end of the world.
'I think a lot of people think a nuclear weapon goes off and everybody gets blown up or disappears.
'The reality is the buildings would collapse and you would be set on fire, which makes it real and scarier.'