monad-task (hackage): Task monad transformer can help refactor event and callback heavy programs into monads via co-routines. The idea is loosely based on Combining Events And Threads For Scalable Network Services, by Peng Li and Steve Zdancewic, in PLDI, 2007. (http://www.cis.upenn.edu/~stevez/papers/abstracts.html#LZ07), but with deterministic and co-operative lightweight threads, also known as co-routines, so that the base monad can be anything ranging from IO to state monads, or your favorite monad transformer stack.
Keywords: bsd3|control|library