Chordify - Chordify turns any music or song (YouTube, Deezer, SoundCloud, MP3) into chords.
ChordU - Extracts chords from any song, integrated YouTube.
Riffstation - The web version is Free and you can learn how to play Chords with Youtube Songs.
Sonic Visualiser - Sonic Visualiser is a program for viewing and analysing the contents of music audio files.
AudioRetoucher - AudioRetoucher is a tool for analyzing music, changing tempo and pitch in real time
Tune Transcriber - Learn and transcribe music for free from your web browser (no install needed).