www.teach-me-piano.com has good basic information about pianos. Here below are links to look at.
Another site, http://www.ptg.org has good sources as well
Great video on how piano keys work with hammer! (via http://www.ptg.org)
pdf on how does piano work?
video about C chord inversions
Video on How piano is made
Virtual Piano Chords, including inversions
Commonly used notation of piano keys, and their related frequencies (logarithmic scale) are available in wikipedia’s pages 1 and 2.