As I was folding a tee shirt the other night using this method, I thought back to my first blush of excitement when I learned this technique thanks to the Internet. That memory made me want to share the thrill with you in case you didn't see it a few years back. I don't know of a way to fold a tee shirt that's faster or more effective at creating a flat, stackable object.
The original Japanese video I saw is here
http://www.youtube.com/watch?v=b5AWQ5aBjgE&feature=related
A slower, more explanatory VideoJug version here. Don't mind the short ad at the beginning. Hang in there.
http://www.youtube.com/watch?v=An0mFZ3enhM&feature=fvw