Earlier today, the Huffington Post released an article online. Two physicists at NYU, David Ruffner and David Grier, have created a working tractor beam. It's a small scale device using two Bessel beam lasers (also invented by the pair) that operates like a conveyor belt, pulling the object toward you.
Just one problem... a ship-mounted one would require enough power in the laser to destroy anything you'd be towing. So, for now, it's small-scale only.