Hoffman Academy
A comprehensive, structured online piano course with free video lessons covering fundamental techniques, music theory, and sight-reading. It's highly recommended by many for its engaging and effective teaching method.
More resources on Piano/Keyboard Basics
How to Really Play the Piano: The Stuff Your Teacher Never Taught You
Self-teaching book for adults who want to play pop, rock, jazz and blues from chord symbols. Covers lead sheets, chord voicings, left-hand accompaniment patterns and rhythm, so readers can build their own arrangements of songs without relying on fully notated scores.
Musopen
Offers free sheet music, recordings, and educational materials. You can find classical pieces, exercises, and resources to support your piano learning journey.
Pianote (YouTube Channel)
A popular YouTube channel offering a vast library of free piano tutorials, tips, and lessons for beginners and intermediate players alike. They cover various topics from basic chords to playing specific songs.