Many ways to do it. So pick one. Or all six.
Via Google, direct to Japanese Red Cross - I recommend this option!
http://www.google.com/crisisresponse/japanquake2011.html
Direct deposit to Japanese Red Cross bank account! ... if you know how.
http://www.jrc.or.jp/english/relief/l4/Vcms4_00002070.html
To American Red Cross, with option to specify distribution to Japan
http://american.redcross.org/site/PageServer?pagename=ntld_main&s_src=RSG000000000&s_subsrc=RCO_ResponseStateSection
Via Amazon, goes to American Red Cross (for Japan?)
http://www.amazon.com/b?ie=UTF8&node=2673660011
Via iTunes, to American Red Cross (for Japan?)
https://buy.itunes.apple.com/WebObjects/MZFinance.woa/wa/buyCharityGiftWizard
Text message, goes to American Red Cross, general funds - my least favorite option
Text REDCROSS to 90999
So there you go.
Now DO IT.
Via Google, direct to Japanese Red Cross - I recommend this option!
http://www.google.com/crisisresponse/japanquake2011.html
Direct deposit to Japanese Red Cross bank account! ... if you know how.
http://www.jrc.or.jp/english/relief/l4/Vcms4_00002070.html
To American Red Cross, with option to specify distribution to Japan
http://american.redcross.org/site/PageServer?pagename=ntld_main&s_src=RSG000000000&s_subsrc=RCO_ResponseStateSection
Via Amazon, goes to American Red Cross (for Japan?)
http://www.amazon.com/b?ie=UTF8&node=2673660011
Via iTunes, to American Red Cross (for Japan?)
https://buy.itunes.apple.com/WebObjects/MZFinance.woa/wa/buyCharityGiftWizard
Text message, goes to American Red Cross, general funds - my least favorite option
Text REDCROSS to 90999
So there you go.
Now DO IT.