Whenever I come I across a Play library I take a note of it here. This collection is neither complete nor have I used all of these libraries. It is mainly used as a point of reference if I want to find some functionality implemented in a Play library.
jroper/erqx an embeddable blog engine for Play Framework.
lifeway/play-redis This plugin provides support for Redis
playframework/play-slick Slick Plugin for Play
julienrf/play-json-derived-codecs Reads, OWrites and OFormat derivation for algebraic data types (sealed traits and case classes, possibly recursive), powered by shapeless.
xdotai/play-json-extensions: +22 field case class formatter and more for play-json
play-products convenient syntactic sugar to combine monoidal structures (e.g. Reads, OWrites, OFormat), powered by shapeless.
jto/validation validation api extracted from play
funnel distributed monitoring system based on a lightweight streaming protocol.
dropwizard/metrics Capturing JVM- and application-level metrics.
agiledigital/kamon-play-2.5.x A temporary implementation of the Kamon Play module that is compatible with Play 2.5.
agiledigital/kamon-play-extensions Kamon extensions for use in Play2 applications.
kenshoo/metrics-play Metrics module for Play2
sief/play-guard Play2 module for rate limiting, based on token bucket algorithm
danielnixon/playwarts WartRemover warts for Play Framework and Slick
check also scala static analysis libraries
iheartradio/play-swagger: Swagger spec generator for play framework
loicdescotte/Play2-HTML5Tags: HTML5 form tags module for Play Framework This module brings client side validation attributes (required, max|min length, …) and formats support (date, number, email, …) to Play templates.