The following groups publish their membership (etc.) information electronically on CTAN archives:
DANTE, Deutschsprachige Anwendervereinigung TeX e.V.
Postfach 101840
D-69008 Heidelberg
Germany
Tel: (+49) 06221 29766
Fax: (+49) 06221 167906
Email: dante@dante.de
Web: http://www.dante.de/
CTAN details: usergrps/dante
Association GUTenberg,
BP 10,
93220 Gagny principal,
France
Email: gut@irisa.fr
Web: http://www.ens.fr/gut/
CTAN details: usergrps/gut
NTG
Postbus 394, 1740AJ Schagen,
The Netherlands
Email: ntg@nic.surfnet.nl
Web: http://www.ntg.nl/
CTAN details: usergrps/ntg
UK TeX Users' Group,
c/o Peter Abbott,
1 Eymore Close,
Selly Oak,
Birmingham B29 4LB
UK
Tel: (+44) 0121 476 2159
Email: UKTuG-Enquiries@tex.ac.uk
Web: http://www.tex.ac.uk/UKTUG/home.html
CTAN details: usergrps/uktug
A listing of all known groups is available as usergrps/info/usergrps.tex