I came across a free site cantoneseclass101.com, they provide free mp3 and transcripts for many many lessons in beginner, intermediate, and advanced. I think, however, they could remove the 10 second English trailer on each MP3 which becomes annoying when looping the audio on your mp3 player.

Edit: Oh wait… It’s not really free… They entice you to upgrade to a basic account $4/month to extend your access to get the full archive of lessons. However, you could always grab everything and not continue the following month.