In a few years the Milkyway Galaxy will collide with the Andromida galaxy.
Here's a nifty simulation.
There is also a documentary on the subject here.
Some say when this happens, two things could happen to the earth depending where we are in the galaxy at the time. We'll either get thrown out of the galaxy or burned to a crisp from the collision of the two black holes. Glad it's a couple hundred million years away. :P