Give blood or money
I'd be surprised if there's anyone on the Web who doesn't yet know that Amazon is waiving their usual fee to allow people to easily donate up to $100 at a time to the Red Cross. Last I checked, people had donated over $4 million through this mechanism. Right now, the page doesn't seem to be working, so I should mention that if you want to donate, you can also donate directly to the Red Cross at their own Web site.
Donate money to Red Cross via Amazon