I'm in for the mastering video (series!) Just tell me where to mail my credit card. (And good luck wringing anything out of it.)
Lots of good ideas in this thread. I am especially intrigued at the thought of working with a recording person, like Ms. Palmer or whomever. Mastering is lots of digital audio knowledge, true, but it's also all about taking all those choices that came before in the process, starting with the chords/lyrics jotted down on the back of a scrap piece of paper, and turning those choices into decisions. The final word on what the recording is to be. So having a solid context (the song project) for the what and whyfors of what is happening inside Sonar during the mastering I think would be insightful as well as useful. Of course then there will be all these requests for different "contexts": do a video with a guitar band, do a video with dubstep, do a video with a polka.
PS (In addition to the "pro" videos, I think cakewalk should do a deal that anyone who posts a "how-to" video about Sonar that garners more than, say, 500 hits (members only? so no sock puppets), earns a gratis upgrade to the next Sonar release.