I found this picture on StumbleUpon the other day and thought I would share it here. It's an image of the antenna galaxies (NGC 4038 and NGC 2039). As you can see in the picture below, this is actually two galaxies that have collided with each other. The two curved trails of stars were formed when the two galaxies began their merger. Eventually the two galaxies will become one, however this isn't expected to occur until 400 million years from now.
Eventually, our own galaxy will merge with the Andromeda galaxy in a similar fashion. I don't think humans will have to worry about that, however, as that won't happen for about 3 billion years!