s&r says, "It doesn't help to learn anything about the piano to play the guitar."

I couldn't disagree more. Music theory is music theory, regardless of instrument. I learned piano as a child before I picked up any other instrument, and that instruction has been priceless in helping me learn to play other instruments more quickly and easily. Early instruction on piano also has been an invaluable aid to my songwriting, virtually all of which I do on guitar. I've lost count of the number of times my guitarist-songwriter friends have expressed envy of me for my knowledge of music theory which they never picked up from learning to play only the guitar.

The reasons I made reference to the diagram of a piano keyboard are that (a) it makes it easy to visualize a C major scale (the white keys) and that (b) it makes it easy to visualize sharps and flats (the black keys).

I linked to the "Chords and Scales on Piano" page because it's a very handy one-spot reference for defining and listening to many different chords. If you know of a similar site that uses a guitar fingerboard, shows the proper fingering for chords and chord inversions, gives the sound of the chord as it should be played, etc., then by all means please post a link here.