More Halo Than You Can Chew
Halo Wars speaks for itself; your standard RTS, in the Halo universe. It's being developed by Ensemble Studios, makers of the Age of Empires franchise. The unnamed project is being made by a studio called Wingnut Interactive (sound familiar), formed by Peter Jackson and Fran Walsh.
I don't know if anyone else has seen the actual logo of Halo 3. Nothing new, but it's something to think about.

There's a bit of symbolism in the new symbol (no pun intended) if you're willing to look.

Maybe we'll get a huge army of Spartans...