Easy Throw-Away Email Addresses
Found on Slashdot on Monday, 27 November 2006

A fellow teaching himself Seam has come up with a clever Web app called 10 Minute Mail. It gives you a valid e-mail address — instantly — for use in registering at Web sites. Ten minutes later (more if you ask), it's gone. You can read mail and reply to it from the page where you create the throw-away address. Limited utility, yes, but easy and free.
That's as new and clever as baked potatoes. I've been using SpamGourmet for over 3.5 years now without any problems; and if the site you're signing up with behaves, your (up to) 9 emails will last for years. Apart from that, most people probably have a bunch of several free email accounts too to keep off spam from your main account.