For MST3K fans, apparently Mike Nelson and the dudes who voiced Tom Servo and Crow (2.0) went ahead and created kind of a cool business model involving do-it-yourself MST3K style features. Basically, you download their commentary track. And they have a little player widget that'll sync the commentary to the DVD (which implies you must have the DVD in your possession already, of course).
The really slick thing about the model is that they don't have to worry about rights, so their commentaries can be as topical as they want and associated with big budget new movies. And at $2.99/track, the commentaries themselves are pretty cheap. It's probably not something I'd spend money on but I bet fans certainly would.
Anyway, the url is:
http://www.rifftrax.com