My Domain is giving away 25 free domains every hour today until 4:00 PM PST. To win one of the domains, simply go to their website's main page, and click on the Domain Giveaway banner. That will take you to a page where you enter your email address, and they will tell you if you've won one of the freebies.
I got my free domain name on my third try at 10:00 AM. It's best to repeatedly click on the banner right after the start of the hour. If you don't win, keep trying!