Humorous books for teenagers

Hi everyone,
I'm presenting a seminar for school teachers and librarians on using humorous books to engage students in literacy. We can find plenty for junior students but would love your feedback on appropriate books (both fiction and non-fiction) for 13-18 yr olds.

Thanks.

Terry Pratchett. It is fantasy with sophisticated satire as well as slapstick. The witch stories might possibly appeal more to girls, but the Sam Vimes stories are full of action and should appeal to both. Going Postal is a particularly good story, featuring the former con man, Moist von Lipwig.
There are 30 books in the Discworld series, which should keep them going for a while. Pratchett dips lightly into the vulgar, which should also appeal.

Fiction:

Jasper Fforde's Thursday Next books: http://www.librarything.com/series/Thursday+Next

The last days of the lacuna cabal

Good omens

Harvard Lampoon just issued a parody of Twilight called Nightlight. Surely some young people would find it amusing.