Well, it started out in 1996 as being based on MultipleChoice 2.0
hacked to email results, but there's not much of that original code 
left. Anyway, QuizTest 3.0 is kind of a cool hack:

http://www.tesol.net/scripts/QuizTest

Supports authorized users per quiz (or not), multiple instructors (or
not), what to show after a quiz, email results to instructor (or not),
statistics for quiz validation, custom html header/footer for each quiz,
web interface to create, edit, or delete quizzes, instructors, or users,
and a whole buncha stuff.  Thought you might be interested to see the
monster that MultipleChoice 2.0 eventually created. :)