東北地方太平洋沖地震
Google crisis response page including their Person Finder tool

This is a good summary of available alarm and warning details as well as transportation status.

The lede has a list of ways you can help

Ushahidi has set up a Japanese page for local coordination

災害情報を集約するためのサイト

More information here.

Some information from the HYOGO Quick Info Secretariat (at the International Relations Division, Hyogo Prefectural Government)
HYOGO Quick Info [Extra Edition/臨時特別号] ～FROM HYOGO PREFECTURE～ （日本語版）

1. Multilingual information for foreign residents (Tohoku Area Pacific Offshore Earthquake Multi-language Support Center)

The Tohoku Area Pacific Offshore Earthquake Multi-language SupportCenter was established. It provides information on the disaster in several languages for foreign residents in Japan. （Japanese, English, Chinese, Korean, Portuguese, Spanish, Tagalog, Indonesian, Vietnamese, Thai）

1. Portal site on policies for foreign residents (Cabinet Office)

The Cabinet Office offers information for foreign residents via the portal site below:

• Japanese
• English
• Portuguese
• Spanish
• You can download a links page to multilingual information websites from the portal site above. （Japanese, English, Portuguese, Spanish）

1. Portal site on earthquake-related information (Japan Meteorological Agency)

The Japan Meteorological Agency offers information on the climate, earthquake and tsunami in the affected areas via the portal site below. The 2011 off the Pacific coast of Tohoku Earthquake Portal (Japan Meteorological Agency)

• Japanese
• English