They're calling it the "Never Ending Pasta Pass," and there are only 1,000 of them available for purchase.
Each pass is good for unlimited pasta and Coca-Cola soft drinks (the pass covers your drink and those of your party at the same table) from the Olive Garden from September 22, 2014 through November 9, 2014.
Unfortunately, they went on sale today and sold out pretty quickly (within 45 minutes and with plenty of errors from the volume of people trying to get one). They're giving away a few via their social media channels including Facebook, Twitter, and Instagram, if you want to try your luck.
If you manage to get your hands on a pass: Consider that their Never Ending Pasta Bowl starts at $9.99, you'd need to make about 10 visits during the promotional period to get your money's worth. Or, if you're looking to stretch your buck (and possibly your stomach) as far as it can go, you could just eat every meal at Olive Garden with the pass until it expires.