I think the 99 Haskell problems are mostly a *terrible* source of short exercises. The problem is that they're exercises translated from Prolog and Lisp. Some of them need substantial "translation" to even make sense in a typed language. Others are problems designed to highlight features Haskell doesn't have. Anyone looking to that list for inspiration will have to do a *lot* of weeding to get something suitable for beginning students, and will probably miss out on the opportunity to use more appropriate problems.