There is a really nifty trick with gmail that allows you to auto label incoming emails.  Say you subscribe to a mailing list.  When they ask for your email address, you would enter something like:

someone+mailinglist@gmail.com

You can then apply a filter to apply a label, mark the message as spam, etc.  Basically gmail ignores everything after the plus sign, and still considers the email as yours.  Talk about thinking outside the box.  Way to go gmail 🙂

The only downside is that some regular expression email validators do not allow plus signs in email addresses 🙁

Via this tip