I don't do financial transactions online. However, I was able to call my bank, Bank of America, and make a direct transfer from my account to an account they have set up just for donations to the Japanese Red Cross. If you don't have an account manager that knows you, you might have to go into the bank to do this.
that describes some of the aspects of the disaster that they're facing: fires, landslides, hypothermia, a large group of elderly displaced persons some of whom are also injured or ill, and over 400 earthquakes since the big one. You might decide, like I did, that you want to give a little more than you were originally planning.
If your bank doesn't have an account set up for donations, suggest they start one, or this page has the banking info for the Japanese Red Cross to make a direct donation: