It's the trailer for Peter Jackson's The Hobbit: An Unexpected Journey, which will be released in December 2012. In it, you'll see Martin Freeman (whom you may know from the British The Office, or from the BBC Sherlock, or — particularly at this time of year — from Love Actually) as Bilbo Baggins, Ian McKellen as Gandalf (some more), and a bunch of guys playing Zinky and Blinky and Grumpy and Sleepy and whoever. (That's a joke. I am not a Tolkien person. I'm just kidding. Don't e-mail me.)
And wait! There's a ring! Nobody tell me whether that's important; I don't want to be spoiled.
I wouldn't begin to actually rush to judgment on this particular trailer — as I said, I am not so much a Middle Earth expert — but I'm sure all of you are eager to do so, so have at it.