Actually nvidia has already drivers for stereoscopic 3D too. I think those work quite much with every game that uses dx or opengl. The thing is you need to render picture '2 times' instead of once and you can do it just overloading some rendering functions.
Example...
http://ioquake3.org/wp/wp-content/uploads/2008/05/stereoscopic3.jpg (Looks quite nice through glasses.)