We made the shirts at home for PyCon FR and that was a LOT of fun, even if we had to work hard to make sure all shirt were ready by the time the event started. We used a silk-screen technique and the output looks really professional. The ink used makes the shirt design last longer than shirts that uses transfer. Although the number of colors is limited.
Have a look at the pictures : http://www.flickr.com/photos/82007723@N00/sets/72157605181699082/
Guess what: some people ordered us some t-shirts for some other events, so some more fun ahead ! :D