Above, "Tokyo Geiger Counter," built with this DIY kit. The location is Tokyo/Kotoku. (thanks, Francesco Fondi)
CNET: "The intensifying nuclear crisis in Japan is raising anxieties on both sides of the Pacific over the potential impacts of radiation exposure, and a relative dearth of official information on radiation levels is leading some to turn to crowdsourced options. (…)
With official estimations of the threat from radiation across Japan changing rapidly and sometimes inconsistent, a number of real-time amateur radiation monitors have popped up online."
Below, a Google Map of "unofficial" radiation monitoring sites.