ArtistWorks provides online music lessons for over 40 different instruments. Subscribers will get access to hundreds of video lessons taught by master musicians.
eMedia Music provided lessons for voice, guitar, bass, piano, and violin, from beginners to intermediate.
EarMaster is a music software company founded by musicians. They sell ear training software and apps for musicians.
Rocket Piano offers piano playing lessons, from beginner to advanced. Signing up for their courses all gets you a lot of freebies.
JamPlay offers guitar and bass lessons through a subscription-based plan. They have thousands of lessons to choose from.