** copied this from my mtbs3d post on this topic **
The demo is a virtual theater. There are others in progress by members on here that are going to have even more impressive features, however there is something that really stuck out at me about this demo.
Forget that it's another theater/video player. What blows my mind about this demo, probably more so than any demo I've tried yet is that due to it's perfect recreation of scale and environment it really fools the brain into feeling like you are at an actual theater.
It has a great little user interface too, pulled up by right-clicking. This is a must try for anyone with a Rift dev kit.
Download from http://uxground.com/
Press the projects tab. It opened in Google drive for me but just do file - save to download locally.
Just download the demo, overwrite movie.avi in the main folder with any .avi movie you have on your local drive (it's really awesome better if you have a 3D SBS avi movie).
If you watch a 3D movie aside from the low pixel resolution of the current Rift it's in my opinion better than 3D theatre experience due to the perfect separation of the images.
I'll provide a couple of SBS sample movie clips you can try at http://dotalore.com/SBSclips.zip
(Please only download this file if you have a Rift, they won't be much use outside of this demo and are only a couple of minutes long.)
You can download more form youtube (filter for 3D content) using VLC to download the file and Pazera mp4 to avi converter to convert it into an AVI file.http://www.youtube.com/watch?v=XU2erJtDZuchttp://www.pazera-software.com/products/mp4-to-avi-converter/
EDIT: mkv people, try the pazera converter and let me know if it helps for you.