Atari's Missile Command is now free-to-play on OMGPOP. Since launching yesterday, players have already logged close to 10,000 hours in game and over a quarter of a million plays.
The title is multiplayer only and players control a single tower. Others plays man the other batteries and help you destroy incoming missiles, but also compete for the high score. Points can be earned to be spent on upgrades improving things like your blast radius, reload speed, and missile supply. Not exactly the classic gameplay you remember.BOOM video 4209
If you want more (or different) Missile Command, there's always the Xbox Live Arcade version.