This is one of the greatest things I have seen in a long time. Culture Vulture has pointed to Harry Potter, the Musical developed by students at the University of Michigan. It’s seriously Broadway (or at least Off-Broadway) quality and is an easy way to kill a LOT of time. Below is Act I, Part 1 – you can click the video to view all parts.
It doesn’t really establish what book it is based on, but it kind of combines several of them. Absolutely brilliant.