The Diaconal Committee of the OPC has set up a disaster response fund to help with the needs in Japan, and other nations as they arise. You can donate at the website HERE or you can send a check or money order to:
Commmittee on Diaconal Ministries
Orthodox Presbyterian Church
607 N. Easton Rd., Bldg. E
Willow Grove, PA 19090-2539
Checks should be made out to "Orthodox Presbyterian Church" and clearly marked for "CDM—Disaster Response."