CoachGuitar uses a visual teaching to learn popular songs on guitar. Each lesson is broken into sections with step-by-step instructions.
iPhone and iPad apps tagged "guitar apps."
PocketGuitar is Amazing
I've seen a lot of great iPhone applictions, but it's been a while since I've seen one as clever and entertaining as PocketGuitar. PocketGuitar turns your iPhone into a virtual guitar, allowing you to strum and press strings as you would on a real guitar.