Pluralsight can, they're videos only, but I've listened to several courses during commute with the iPad out of sight and I can get most of the material being discussed from just the audio. A lot of the iTunesU stuff is audio only, or the same as Pluralsight, can be understood without needing the video.

Coursara not so much. There are assignments and code projects in all the courses I've so far done with them, so that's far more something that needs dedicated study time.