How to: Concurrency and Parallelism
* [Concurrent Ruby](https://github.com/ruby-concurrency/concurrent-ruby) - Modern concurrency tools including agents, futures, promises, thread pools, supervisors, and more. Inspired by Erlang, Clojure, Scala, Go, Java, JavaScript, and classic concurrency patterns.
* [EventMachine](https://github.com/eventmachine/eventmachine) - An event-driven I/O and lightweight concurrency library for Ruby.
* [forkoff](https://github.com/ahoward/forkoff) - brain-dead simple parallel processing for ruby.
* [Parallel](https://github.com/grosser/parallel) - Run any code in parallel Processes (> use all CPUs) or Threads (> speedup blocking operations). Best suited for map-reduce or e.g. parallel downloads/uploads.
* [Polyphony](https://github.com/digital-fabric/polyphony) - Fine-grained concurrency for Ruby.