These are a few links you may find useful. The list is far from complete and in no particular order but should provide some good starting points.

NSA2009 - The  35th National Stereoscopic Association annual convention.

Organizations:

The National Stereoscopic Association - National 3D organization.

International Stereoscopic Union - An international stereo group.

Photographic Society of America - Stereo Division - Just what it says.

Atlanta Stereographic Association - Local Atlanta stereo club

Cascade Stereoscopic Club - Local Portland Oregon stereo club.

Stereo Club of Southern California - Local Los Angeles stereo club.

Amateur Photographic Exchange Club (APEC) - Stereo view exchange club

Digital Stereoview Exchange Club (DSEC) - Stereo view exchange club for "digital format"

Interesting 3D Sites:

20th Century 3-D - Information on old viewers and views.

3D by Dan Shelley - Good link site with lots of stereo related information.

Boris Starosta - 3D images some for sale.

Phantomphotos - Phantogram site

Stereoscopy.com - Good information source and gateway site.

Terry Wilson - 3D images for sale including Phantograms

View Master Homepage - "View Master" related information with some sales.

3D Supplies and Equipment:

3D Concepts - Suppliers of RBT cameras, mounts and projectors.

3D Stereo.Com - Suppliers of 3D related material.

Berezin Stereo Photography Products - Manufacturer and supplier of 3D related material.

Dr T's Stereoscopic 3D Site - 3D books and repair services.

Graphic Media Research - Manufacturer of the "PokeScope" viewer and software.

Reel 3-D Enterprises - One of, if not the oldest, suppliers of 3D related material.

Rocky Mountain Memories - Suppliers of "Spicer" mounts and other 3D material.

The Stereo Store - Supplier of 3D material, slide duplication and video services.