The Stereoscopic Society
The Stereoscopic Society is certainly the oldest 3D society in the world. The Society has been in existence since 1893 and its objectives are to foster the practice, enjoyment, and advancement of all forms of stereoscopy - pictures in three dimensions.
The Society offers a warm welcome as an active member or otherwise; the annual subscription payable to The Stereoscopic Society for 2009 is £21 for members resident within the UK, £23 for members in mainland Europe (outside the UK), and £26 for members living outside Europe. New members are welcome with or without experience in stereo photography.
The SS website is here. You will find info on how to register, reports from the last meetings, and many other useful 3D related information.