Check out this article from Bad Astronomy. By far the most interesting thing I've read in a long time. In brief, a star system has been found where one member, a star so massive that the atoms themselves collapse into one gigantic nucleus many miles across, is rotating and orbiting at mind boggling speeds around a star so large it would dwarf the sun. The large star is literally draining into the small massive one due to the incredible gravitational and tidal forces. Really weird stuff, science fiction can't compete with reality.
This kind of thing fascinates me because the masses, sizes, speeds and forces are so far removed from anything we are capable of understanding, even the analogies that try to convey a sense of scale challenge our imaginations and expand our cognitive horizons.