Did you pick up a retail copy of God of War: Ascension? If so, you may have noticed that a demo for The Last of Us would be made available, although not at the time of Ascension's launch. Today's the day that demo goes up so here's a reminder for those of you with a copy of the game.
Either grab the insert that came with the case and plug the number into PSN or put Ascension in your system and click "The Last of Us Early Access" from the menu. Either method should allow you to download and play the demo, which features the Outskirts level.
When the demo supposedly went live (around 10 PM) many users took to the PS Blog to say the Store wasn't letting them download it. Apparently the issue has been fixed for most, but if you receive an error then try downloading The Last of Us' demo tomorrow.