There are a lot of charities doing good work in Japan to which you can donate cash. But if you'd like to do contribute something tangible, you can put together and send a care package for affected kids.
The Misawa Girl Scouts are organizing a backpack/care package drive for kids displaced by the disaster. You can send a complete package inside a backpack or backpacks/care package materials by themselves.
The Girl Scout troop will be collecting care packages until May 15th after which they'll distribute them. They say that priority mail from they U.S. takes about two weeks so that still leaves you several weeks to get everything together.
E doesn't know about the tragedy in Japan (and wouldn't understand even if I tried to explain) but if you have older kids this could be a great opportunity to get them involved. I bet they'd have fun picking out items to include in the care package.
For a list of recommended items, shipping info, and other details see here.
If you live here in UT county and want to participate let me know and maybe we can bundle our care packages together for shipping.