I was recently pointed to some awesome simulations involving galaxies and what might happen when they collide. The simulations were created on a super computer and enable us to view what might happen within the period of several billion years in just a few minutes. A particularly interesting one shows the mergence of the Milky Way with the Andromeda galaxy which is predicted to start to occur in the next 3-4 billion years or so. Some of the other simulations involve hundreds of galaxies interacting with each other. The movies are pretty big so you’ll need a decent internet connection to download them.