iTunes link: TouchChords – Free
There are plenty of apps out there that aim to help guitarists improve their playing skills, but TouchChords is definitely the best of the free options. It started out as a way to help guitarists learn more chords, but it has now evolved well beyond that.
Its core feature is still the chord library. This not only shows diagrams of the fretting position for the chords, but can also be set to display an overlay of a hand to indicate exactly how your fingers should be positioned to properly form the chord. There are now also practice lessons built-in to help you get to grips with using the chords for different playing styles and there’s also a limited guitar tab feature that has lessons on how to play some famous riffs.
If you play guitar you should have this excellent app loaded on your phone.