There are 2 repositories under monad-transformers topic.
C# functional language extensions - a base class library for functional programming
Lambda the ultimate Pattern Factory: FP, Haskell, Typeclassopedia vs Software Design Patterns
Extensions for F#
Functional programming great resources
A mini Scala utility library
A framework to create embedded Domain-Specific Languages in Scala
Monadic effects and equational reasonig in Coq
Resource Acquisition Is Initialization
Memoization monad transformer
Solutions to exercises from the book Haskell Programming
Scala library for nice business logic oriented, for-comprehension-style error handling
Transformerless monads for Puresript
A correct Scheme interpreter derived from the R5RS spec's formal semantics, written in Haskell.
Monad transformers for exception handling
Monad transformers for the persistent library
Toy example — How can GHC optimize monad transformers?
Stricter drop in replacements for WriterT and RWST
Compatibility package for old transformers: Stricter drop in replacements for WriterT and RWST
Settlers of Catan in Haskell with a Web Browser GUI
A clone of monad-control in purescript
Introduction into functional dependency injection with Reader monad.
MTL, but without the MT