Estey Organs
www.esteyorgan.com/
La route des orgues de France
www.culture.fr/culture/orgues/
The British Institute of Organ Studies
www.bios.org.uk/
The American Guild of Organists
www.agohq.org/
Organ Historical Society Catalogue
www.ohscatalog.org/
PIPORG-L
www.albany.edu/piporg-l/
Encyclopaedia of Organ stops
www.organstops.org/
Osiris Organ Stoplist Archive
www.wu-wien.ac.at/ftp/pub/earlym-l/organs/