A quote from http://taspring.clan-sy.com/download.php :
"What is Spring?
Spring is a project to create the best RTS ever (no joke). There are three principle goals which we hope to achieve.
1. Reach a stage where TA Spring can flawlessly execute most of Total Annihilation's original gameplay, with its original units in their original format.
2. Add new features as we see fit, fix bugs, and release new versions when we feel it is appropriate to do so.
3. Support the mod community as we see fit.
4. Improving the already fine original TA Interface in a way that the Players will have more tatctical Options, more Control, more Comfort and still don`t get lost, as long as they are willing to learn."
It's like Supreme Commander... But it's playable now and don't cost a thing. You can also download it from their site...