How to Learn 1/3 of the Ukulele Fingerboard in Minutes (and master the rest as well) One of the first things Mike did on his "Lamb Chop Ukulele Cookin'" blog was to publish this very helpful guide that shows players how to master the notes on the ukulele fretboard.  Click on the link above to build your knowledge and prove that you really can master 1/3 of the notes on the ukulele in a just few minutes!

Aldrine Guerrero's Ukulele Minutes Theory Collection
Ukuleleunderground's Aldrine Guerreo has made some incredible videos that, within two to three minutes, explain tons of important theory in an easy-to-understand, easy-to-access way.  Updated as of July 2010.

Nothing Could Be Finder...Chord Finders on the Internet
Not sure if these are products (they're free) or instruction, but I put them under both categories as I think this is a helpful guide to some tuners and chord finders out there online.