Alternatives and similar repositories for each:

Users that are interested in each are comparing it to the libraries listed below

• qifun / stateless-future
  Asynchronous programming in fully featured Scala syntax.
  ☆177Updated 8 years ago
• ThoughtWorksInc / Dsl.scala
  A framework to create embedded Domain-Specific Languages in Scala
  ☆254Updated 2 months ago
• scala / collection-strawman
  Implementation of the new Scala 2.13 Collections
  ☆199Updated 6 years ago
• monadless / monadless
  Syntactic sugar for monad composition in Scala
  ☆279Updated 7 months ago
• nbronson / scala-stm
  A library-based Software Transactional Memory (STM) for Scala, coupled with transactional sets and maps
  ☆251Updated last year
• lihaoyi / Scalatex
  Programmable, Typesafe Document Generation
  ☆291Updated 5 years ago
• hanabix / config-annotation
  A refactor-friendly way to use typesafe's config by scala macro annotation
  ☆105Updated 6 months ago
• ktoso / scala-types-of-types
  Scala's Types of Types
  ☆151Updated 6 years ago
• scalapuzzlers / scalapuzzlers.github.com
  Github Pages behind scalapuzzlers.com
  ☆161Updated 4 years ago
• zio-archive / zio-actors
  A high-performance, purely-functional library for building, composing, and supervising typed actors based on ZIO
  ☆270Updated 7 months ago
• fosskers / scalaz-and-cats
  Usage examples and benchmarks between Scalaz and Cats (w/ Haskell ground-truth).
  ☆487Updated 3 years ago
• Log4s / log4s
  High-performance SLF4J wrapper for Scala.
  ☆171Updated last year
• argonaut-io / argonaut
  Purely functional JSON parser and library in scala.
  ☆545Updated last week
• jsuereth / scala-arm
  This project aims to be the Scala Incubator project for Automatic-Resource-Management in the scala library
  ☆548Updated 4 years ago
• lihaoyi / autowire
  Macros for simple/safe RPCs between Scala applications, including ScalaJS/ScalaJVM
  ☆379Updated 3 years ago
• Algomancer / Full-Stack-Scala-Starter
  Play 2.5, ScalaJS, Binding.scala starter project.
  ☆195Updated 7 years ago
• scalameter / scalameter
  Microbenchmarking and performance regression testing framework for the JVM platform.
  ☆511Updated 2 years ago
• ThoughtWorksInc / sbt-best-practice
  Configure common build settings for a Scala project
  ☆57Updated 2 months ago
• typelevel / cats-collections
  Data structures for pure functional programming in Scala
  ☆560Updated last week
• Centaur / scalaconsole
  Scala REPL in a GUI
  ☆74Updated 5 years ago
• traneio / arrows
  High-performance Arrow and Task in Scala
  ☆240Updated 6 years ago
• scalacenter / macros
  Archived - Scala Macros
  ☆123Updated 6 years ago
• lightbend-labs / mima
  A tool for catching binary incompatibility in Scala
  ☆468Updated last week
• storm-enroute / coroutines
  Scala coroutines implementation.
  ☆163Updated 7 years ago
• scalamacros / paradise
  (No longer actively maintained.)
  ☆157Updated 6 months ago
• typelevel / kind-projector
  Compiler plugin for making type lambdas (type projections) easier to write
  ☆924Updated last month
• com-lihaoyi / sourcecode
  Scala library providing "source" metadata to your program, similar to Python's __name__, C++'s __LINE__ or Ruby's __FILE__.
  ☆527Updated 4 months ago
• frees-io / freestyle
  A cohesive & pragmatic framework of FP centric Scala libraries
  ☆615Updated 5 years ago
• ThoughtWorksInc / Compute.scala
  Scientific computing with N-dimensional arrays
  ☆200Updated 7 months ago
• underscoreio / shapeless-guide-code
  Example code to accompany shapeless-guide.
  ☆133Updated 2 years ago