Check out http://www.mmospacewar.com/. I made a few changes to mmoasteroids.com to make it behave more like the DOS version of Spacewar. Unfortunately, Firebase isn't available for another 1 day 18 hours 18 minutes and 10 seconds yet (http://www.firebase.com), so anyone who plays this will share the world and scoreboard with MMO Asteroids for now. (Hopefully this doesn't present a problem to the guy who created MMOAsteroids; there are already plenty of cheaters on there anyway.)
New features: warp (press 'z') and instead of instant death you have an energy which gets depleted by using thrust, colliding with other ships/bullets, and warping.