Can I Donate Money Anonymously on the Internet?

OK, hivemind, here’s a question for you: is it possible to donate money anonymously other than by sending wads of cash to people? I sometimes want to contribute to a cause without having my name attached, either because I don’t want to be put on an eternal mailing list for further donations or because I don’t want the recipient to feel obligated to me. Those may or may not be good reasons, but as Donald Rumsfeld once said, you go to war with the reasons you have, not the reasons you wish you had.

So….is there any convenient way to do this? I suppose anonymous money orders or certified checks would work in some cases. How about electronically? Does PayPal have an option to hide payor information? What are my options here?