This fall I'll be teaching a half-credit introduction to Haskell to
some undergrads.  As a final project I am thinking of giving them the
option of (instead of developing some program/project of their own)
contributing to an existing open-source Haskell project.  Of course,
this requires the existence of projects they could contribute to.  I'm
sure they exist, but need your help to figure out what they are.  So,
do you maintain, or know of, any projects with the following
characteristics?