I think the maps are especially useful but lots of good info available at the Google Crisis Response for the 2011 Japanese Earthquake/Tsunami. Google did a person finder for the Christchurch Earthquake, too, but this really encompasses much more information. Google has put together a list of resources for the 2011 Japanese Earthquake and tsunami, including a link to the person finder in English and Japanese).
Other resources include links to travel, maps(showing shelters, affected locations and more), latest news, and official information.
(and it’s a really interesting use of technology, social media, and harvesting data from a variety of sources… I will write more on the aspect later)