Jürgen Hiller's Site
Jürgen Hiller also makes custom trautoniums to order
Trautonist's channel on youtube, has many videos about the trautonium
Doepfer.de have a page dedicated to the trautonium, it has useful information on how the instrument functioned. One may purchase modules that recreate the sound generation. The manual that Doepfer now offers has an improved pressure sensor, which is just as well because the original was, er, difficult in my experience.
Obsolete has a page with history and brief mp3 examples.
A page with an hommage to Oskar Sala by Pete Namlook, it includes an obituary and discography of Erdenklang releases.http://www.furious.com/perfect/ohm/oskarsala.html