Bootstrapped algebraic data types for Elixir
Error & exception handling helpers for Elixir
XML parser for Elixir (based on Erlsom)
Helpers for debugging & inspecting code flow
Helpers for defining operators
Exceptional error/exception helpers for Phoenix
Common combinators for Elixir
(Semi-)principled type classes for Elixir
Monads and other dark magic (monoids, functors, traversables, &c)