Gunner at No quarters has found an interesting site for those who seek anonymity. dodgeit is a free, read-only email site. Make up a user ID, hand it out to people, go here from anywhere on the web (using the cloak or Anonymizer, perhaps?) to check for messages. A caveat; anyone who knows the ID can check the mailbox.
I can see a lot of uses for this, good and bad–as with most technology. A cool tool.