Threadless screenprint, mostly with plastisol ink I think.
The core hasn't really changed. Screenprinting is still king, but now there are more options for ultra small runs (1-20), and technology that may take over one day (
DTG). But for now... old school still works just fine if that's what you know.
If you want to know more about
DTG, dye sublimation, etc. try reading some threads in each of those sections on the forums.