You can donate money via your Paypal account. Go to the Paypal homepage and there is a large button on the right: Donate to the Tsunami Relief Effort, UNICEF (part of DEC I believe). If you click on the button it will tell you more about it.

This is great for sellers wishing to donate proceeds of sales.

I only hope that Paypal are not deducting anything from the money donated as they do on sellers receiving money.