There has been some confusion and debate about how and who to donate to. 

I personally suggest going through Paypal.

Paypal (along with Missionfish) allows you to donate to an organization of your choice giving relief aid to Japan. That way if you have philosophical problems donating to one group, you can donate to others.

You can access it from 
https://www.paypal.com/
direct link
https://www.paypal-donations.com/pp-charity/web.us/campaign.jsp?cid=-12

Be careful of donation scams. Make sure you go to a relief organization's official website for accepting donations, and verify who is getting your $

Huffington Post also has a huge list of donation Options here:

http://www.huffingtonpost.com/2011/03/11/how-to-help-japan-earthquake-relief_n_834484.html

And lastly, not that I want to toot my own horn here, but I will be donation %25 of all commision funds to Japanese relief efforts. So if you order a commision or buy the forthcoming art I'll use paypal's service to forward the funds.