Two of my Game Programming students from last fall, Nathan Willingham and Seth Ringling, developed a real-time strategy game called Scatha for their final project. Nathan and Seth put some more time and effort into the project and have now released the Xbox 360 game for purchase.
I'm really proud of the effort these guys have put into their first Xbox game. Not only did they write every line of code in the game, they also created all the graphics. If you enjoy playing RTS games, I think you're going to enjoy playing Scatha.
Update on 7/22/10:
Seth and Nathan have now released a second game called Four Corners and are working on a third title. Their game company is called Living Creature Studios.