United Methodist http://www.gbgm-umc.org/umcor/
Presbyterian (USA) http://www.pcusa.org/ministries/pda/japan/
Episcopal Relief and Development, http://www.er-d.org/
Christian Church (Disciples of Christ) http://www.weekofcompassion.org/
American Red Cross http://www.redcross.org
This is not a comprehensive list. Colleagues from other traditions not named here might want to post their information to the community as well.
Please pray for this nation and all those who have suffered tragic losses and injury during this disaster, which continues to unfold.