Thought this was interesting. I'm sure we'll be hearing a lot about it soon.
http://www.nasa.gov/content/goddard/.../#.UnmREhCKIQk
This video explains it well:
http://www.space.com/22035-will-come...rth-video.html
It will be closest to the Earth December 26th but will pass at a safe distance.
However we may pass through it's dust years later.