There was an article in 'Welt am Sonntag' (German Sunday paper) yesterday about cave diving and some training courses provided by Professional Association for Technical Diving.  The links quoted in the paper may be of interest (some have english content):

http://www.patd.de/index1.htm
http://zauberwelten.com/index.html
http://hoehlentauchfuehrer.de/
http://cavediving.de/