Via Deals We Like. Enter the Go For The Emerald sweepstakes here and you can have a chance the win two OneWorld Explorer tickets in business class. These are basically round-the-world tickets that can be used on a range of OneWorld Alliance member airlines.
In addition, the first 20,000 people who enter will receive 1,000 American Airlines AAdvantage miles! All you have to do is play a simple game that details some of the benefits of OneWorld Alliance elite status. When I entered about 10 minutes ago, they were already up to 12,000 entries, so act fast! I don't expect the 1,000 AAdvantage miles offer to last for more than another hour.
The website is a little buggy, so make sure you click all the way through to the end, where you can enter your name, email, and AAdvantage account number. You should see a confirmation page afterwards, and you should also receive a confirmation email.
EDIT: Looks like the 20,000 entries have already been reached. You can still play the game and enter, but there are no guarantees that you will receive the 1,000 AAdvantage miles.