You actually get more address variations than just “yourusername@gmail.com,” all of which get delivered to you. You can put a plus (”+”) sign and any combination of words or numbers after your name, like changing hikingfan@gmail.com to hikingfan+mailinglists@gmail.com or hikingfan+junk@gmail.com. Then you can easily add a filter to label and/or archive messages sent to the variations.

This is brilliant for finding the source of your spam. If you sign up for an account with a website, and you’re unsure about their spam policy, then use something like yourusername+sourcewebsite@gmail.com. All the mail will still come to you, but if you start getting spammed to that address, then you know who gave it out. And it’s easy to filter mails from facebook, youtube etc (yourusername+facebook@gmail.com).