Will Google never cease to provide us with numerous ways to waste our lives?
The latest Chrome Experiment, Cube Slam, is a nifty twist on the pong classic, offering 3D visuals and some pretty awesome/menacing power-ups. Available for both single and multiplayer, it's highly worth checking out. Just make sure you have an hour or two to spare.
It is also probably the only game (other than that of hunter/prey) where you are likely to be defeated by a bear.