My mail is hosted on servers running Postfix that I control, so this won't work for everybody.

In main.cf:

  virtual_alias_maps = hash:/etc/postfix/db/virtual_aliases

This file is in the same standard aliases(5) file format:

  [email protected]          [email protected]

I started doing this when I moved all of my mail off of Google. It has the advantage (over [email protected]) that it doesn't reveal my real mailbox. It does very quickly reveal who shares/sells my e-mail address, though. When that happens, it's simply a matter of deleting the alias from the file.