Here is a great article from Mashable.com on social/digital tools to aid in relief efforts in Japan. This includes links to the code from Hellobar.com to add a red donation bar to the top of your wesite.
The Red Cross text donation plan still seems to be the quickest way to help:
The American Red Cross has once again launched a texting campaign to raise money for relief efforts in the Pacific region. Last year, the Red Cross was able to raise over $20 million for Haiti relief through simple text donations.
If you would like to donate to the American Red Cross for Japan Earthquake Relief, just text REDCROSS to 90999. Each text will provide $10 towards the Red Cross’s humanitarian efforts.