Here's a collection of links to the websites of people or organisations that I know or am associated with.
InnerSpace Systems Corp. - Makers of the Megalodon rebreather, the same unit I use.
Eagle's Nest Technical Divers - Home of Larry and Debra Green. One of the permanent fixtures in the cave diving community, and makes some very nice reels.
NACD - National Association of Cave Divers.
IANTD Austria - Website by Horst Schmid.
Umex - Dive store in Vienna, Austria. Owned by Arnold Gerstl and Horst Schmid. I do frequent trips with these guys.