As of March 18, 2011, US Embassy Tokyo advises that they are only processing emergency visa cases due to the recent events in Japan. Some nonimmigrant visa applicants with approaching deadlines, such as students, and individuals already scheduled for nonimmigrant work visa appointments may keep their interview appointments. See below for more detail.
Finally, US Embassy Tokyo advises that they can assist in emergency cases only under very limited circumstances, and they hope to resume normal operations as soon as possible. Please continue to monitor their website for updates.