A live journal community called Help Japan has been organized and will be doing an auction to raise money for relief efforts. In the meanwhile they will be updating this post with the contact information for reputable aid groups and how to give:
http://community.livejournal.com/help_japan/740.html Note: the 90999 number to donate to the Red Cross via text works in the US but in Canada you need to use 30333.
Also, Maureen Johnson has organized a drawing for prizes for those donating to Shelterbox
http://www.maureenjohnsonbooks.com/2011/03/11/shelterbox-in-japan/
If you like the comic strip Dork Tower all proceeds from purchases of the first collection, Dork Covenant, at DriveThruRPG this month will be donated to relief efforts.
http://rpg.drivethrustuff.com/product_info.php?products_id=89298