"Good improvisation communicates harmonic progression melodically. Effective melodies manipulate harmonic content through the use of guide tones and preparatory gravity notes, masterfully woven in systematic tension, release, and transparent harmonic definition."
You're probably already familiar with the legacy of John Baxter. His online resource Mandozine archives some of the best information, interviews, and TEF for mandolin available. You might already own his Deluxe Encyclopedia of Mandolin Chords from Mel Bay.
He's pioneering an iPad application that creates chord sheets for guitar, ukulele, mandolin, and other instruments. In order to bring the final product to the market, he's enlisted the help of investors, donors, and customers through a page on the Indiegogo site. $5, $10, $75 and up, you can be a part of fretboard educational history.
Disclaimer: In the 'Information Age' of the 21st Century,
any fool with a computer, a modem, and an idea can
become a self-professed 'expert." This site does not
come equipped with 'discernment.'