Outstanding. Easy to understand and lots of cool interactive links showing how Bach's music works.
When I teach, I often have my students play the works of Bach for ear training practice and learning how to develop a bass line which compliments the melody while remaining functionally sound. This website (as well as the 371 Chorales and 69 chorale melodies with Figured Bass (edited by Riemenschneider) are great tools.
Just remember Jazz and Blues theory are governed by slightly different principles, but it all interrelates.