A-ha! I have at last found another example of litvlog singalongs online. Check out the youtube channel for historyteachers, which has 48 different music videos exploring different parts of history, which they describe as being "Music videos we made to make teaching history more fun." (Obviously not all of them are literary, but enough of them are to be well worth checking out even if you're not a history buff.)
What makes them noteworthy, though, is that (a) the videos are incredibly well made; and (b) the videos are all pretty different from each other.
I freaking love this kind of stuff.