Tabs Lite - An ad-free open source guitar tablature application using an existing popular tabs database. Built for speed and simplicity.
ChordU - Extracts chords from any song, integrated YouTube.
Guitar Dashboard - Open-source interactive music theory for guitarists.
yalp.io - Automatic chords extraction from mp3 and YouTube
UltimateGuitar.com - Learn how to play your favourite songs on guitar or ukulele
Guitaa.com - Turn ANY song into chords, play along with interactive chords and diagram, transpose, loop, tempo control.