Volunteer in Japan
See Wwoofing in Japan: Cultural Immersion Through Volunteer Vacations by Matt Uchimaru for one participant report.
American Red Cross
Contribute and Volunteer to the American Red Cross to help the decimated regions of Japan.
Visit: www.redcross.org/en/volunteer, and sticking to cash donations for now may be the most effective use of your time and money for a variety of reasons.
Service Civil International Workcamps SCI US
SCI is an exchange organization that sends volunteers on 2-3 week international work projects and long term 3-12 month opportunities in over 50 countries, including Japan. The $250 application fee covers lodging, meals, and minimal health insurance. SCI promotes voluntary service to impact social, environmental and humanitarian issues.
Visit: www.sci-ivs.org for an application.
U.S. contact provides list of 40-50 organic host farmers in Japan to members and can assist with teaching internships and visas. Membership costs $40.
Contact: email@example.com, www.wwoofjapan.com.