justinguitar.com...There are many hundreds of free guitar lessons here, most with video and audio
musictheory.net...explore the foundations of music
ultimate-guitar.com...mainly a shop?
playbassnow.com...Lessons, Licks and Low notes with MarloweDK
howtoplaypiano.ca...Andrew Furmanczyk Piano Academy
Andrew Furmanczyk Piano Academy on YouTube...This channel is focused on providing 100% free musical education for people who have a passion to learn music, but might not be able to afford it or are curious about music.
teoria.com...Music Theory Web