• Japan Meteorological Agency Tsunami Warnings/Advisories
• Pacific Tsunami Warning Center
• Prime Minister of Japan and His Cabinet (Japanese)

Disaster bulletin board

• NTT docomo Disaster message board
• KDDI Disaster message board
• SoftBank Disaster message board 
• Person Finder: 2011 Japan Earthquake

• Contacting U.S. citizens in Japan
  U.S. citizens in Japan who need help, or people concerned about U.S. citizens there, can email the State Department here or call 1-888-407-4747 or 202-647-5225.
• American Red Cross
  If you'd like to donate to the Red Cross efforts, text "redcross" to 90999, and you can make a $10 donation to the organization. Or visit their website for more information.
• World Vision
  The humanitarian group is rushing personnel into the affected areas and providing food, water, medical supplies and shelter for victims.
• Globalgiving.com - Japan Earthquake and Tsunami Relief Fund
  Globalgiving.com has established the Japan Earthquake and Tsunami Relief Fund. They will disburse funds to organizations providing aid and relief to victims.
• American Humane Association
  The "other" victims of this devastating disaster; donate now to the American Humane Association - they've set up a relief fund for rescuing animals. Donations will help provide shelter and care.