I already have this game on CD, but I have a few friends that I'll be giving the news to. Total Annihilation is a classic RTS that I'm surprised hasn't been ported or sequalized en masse. But perhaps that's for the best, so as not to ruin the fun and furious "build-units-and-make-everything-explodey" gameplay. It's got a story, but that's all it really amounts to: building an army from the ground up (including ground, sea, and air units) as quickly as you can to destroy your enemies.
The game still has a pretty strong community following it that make custom fixes, mods, units, weapons, etc. I have a terrible, terrible habit of never being able to finish any RTS (and to be fair, Total Annihilation is no exception), but this game is one of the few that I keep coming back to and playing around in.
Check it out.