Unlimited Gmail aliases

A helpful tip from Google, if you didn't know about this already:
Gmail doesn't offer traditional aliases, but you can receive messages sent to your.username+any.alias@gmail.com. For example, messages sent to jane.doe+notes@gmail.com are delivered to jane.doe@gmail.com. You can set up filters to automatically direct these messages to Trash, apply a label or star, skip the inbox, or forward to another email account.
For me at least, this is a useful way of assigning custom email addresses to different services I use, particularly if I don't trust them.  If I get spam directed to one of these addresses, it's both simple to filter out, and to determine which service sold my email address to a third party.