There are countless articles on websites regarding the organ. If there is one that has caught your eye, do please share it with me so it can be added to the list.
A Brief Guide to the Pipe Organ
A Dictionary of Music and Musicians/Organ
A Young Persons Guide to the Organ
Best Organ Pieces in Existence – Compiled by Classic FM
Harrison and Harrison Glossary of Organ Terminology
The World’s Most Spectacular Organs