The Piano Buyer is a supplement to Larry Fine's excellent
guide "The Piano Book". You can read the whole
thing online (free), search the database and it's full
of the information anyone needs to effectively find
the right piano for their needs. Highly recommended.
A good explanation of how a piano action works
humidity control systems
Information on the systems that protect your piano from
excess humidity and dryness
about Piano in the Theater
very good general information page on the history of
the piano, with links to other interesting pages.
Piano Education Resource Guide
An interesting collection of piano resources on everything
from learning and teaching piano to tuning and genre