These are just a few links, but there are other options besides donating.
Doctors Without Borders/Medecins Sans Frontieres
Person Finder: 2011 Japan Earthquake
NOAA Pacific Tsunami Warning Center
If you have tech skills, Crisis Commons is seeking volunteers to monitor the situation in the Pacific Rim, gather data and identify needs stipulated by local agencies and humanitarian aid organizations that can be addressed through collaborative online software development. Honshu Quake
Adventist Development and Relief Agency International’s Response to Japan Tsunami
All Hands Volunteers’s Response to Japan Tsunami
American Jewish Joint Distribution Committee’s Response to Japan Tsunami
International Rescue Committee’s Response to Japan Tsunami
…or create your own way.
WANDERLUST 