milessabin/shapeless

Generic programming for Scala

scopt/scopt

command line options parsing for Scala

scala/scala-parser-combinators

simple combinator-based parsing for Scala. formerly part of the Scala standard library, now a separate community-maintained module

outr/scribe

Practical logging framework that doesn't require any other logging framework and can be completely configured programmatically.

typelevel/machinist

Spire's macros for zero-cost operator enrichment

suzaku-io/boopickle

Binary serialization library for efficient network communication

monix/minitest

The super light testing library for Scala and Scala.js

propensive/contextual

Contextual

scodec/scodec-bits

Provides immutable datatypes for working with bits and bytes

lihaoyi/pprint

Pretty-printing value, types and type-signatures in Scala

alexarchambault/argonaut-shapeless

Automatic argonaut codec derivation with shapeless

outr/reactify

The first and only true Functional Reactive Programming framework for Scala.

adamw/quicklens

Modify deeply nested case class fields

typelevel/paiges

an implementation of Wadler's a prettier printer

marklister/base64

Tiny scala-js compatible base64 encoder/decoder written in idiomatic scala. Available on Maven central.

msgpack4z/msgpack4z-core

typeclass based functional msgpack serializer/deserializer for Scala. support scala.js and scala-native / msgpack.org[Scala]

jokade/slogging

A Typesafe-logging (and slf4j) compatible logging library based on macros for Scala/JVM, Scala.js, and Scala Native

scalapb/lenses

Tiny lenses library with focus on ease of use.

outr/perfolation

Performance focused interpolation

eed3si9n/expecty

Power assertions (as known from Groovy and Spock) for the Scala language.