For anyone that hasn't seen it and just wants to know the ending: Liam Neeson is the last alive and in the middle of the wolves' den. He tapes a knife to one hand and broken bottles to the other, runs at the alpha wolf and the movie ends.
I thought it was great, even though a lot of people don't like those types of endings. Also, there's a scene after the credits which shows the alpha wolf lying on the ground while Liam Neeson is laying up against him. The wolf is breathing, but dying, and since the camera shot is from the back, we don't really know if Liam was alive or dead.
Personally, I like to think that the alpha wolf died, the other wolves run away and Liam is saved.