"Scalaz is a Scala library for functional programming. It provides purely functional data structures to complement those from the Scala standard library. It defines a set of foundational type classes (e.g. Functor, Monad) and corresponding instances for a large number of data structures."
"If you are a former Java developer and have become a Scala fanboy like me, you will probably sooner or later encounter terms like monad, functor or other mysteries from the realm of category theory which make you feel like a little dummkopf (screamingly funny for a German like me, according to www.dict.cc this seems to be a proper English verb)."
"The goal of this document is to serve as a starting point for the student of Haskell wishing to gain a firm grasp of its standard type classes. The essentials of each type class are introduced, with examples, commentary, and extensive references for further reading."