Dewey's Read-a-thon. Sounds like it could get intense: "The most hardcore among us will stay up the entire 24 hours and do nothing but read and update, even going so far as to skip showering and eat meals while reading."
I do loves me some books, but I think I might love sleep and food just as much, so I'm not sure I'm such a good candidate for this one *grin*!
Though to be fair, rule #8 is: "In general, don’t be a masochist. This is supposed to be fun! And if anything about the challenge makes you start picturing us with little devil horns and wanting to strangle us, please stop and change it so that it works for you. Or, you know, go ahead and scream TO HELL WITH THIS CHALLENGE and go to sleep. We don’t want sleep deprivation making you hate your friendly read-a-thon organizers."
Anyway, very cute idea (at least with some eating and sleeping breaks somewhere in there) - they even get people to sign up to be 'cheerleaders' for the readers!