- Bundler - Bundler maintains a consistent environment for ruby applications. It tracks an application's code and the rubygems it needs to run, so that an application will always have the exact gems (and versions) that it needs to run.
- rabl - General ruby templating with json, bson, xml, plist and msgpack support
- Thin - Very fast and lightweight Ruby web server
- Unicorn - Unicorn is an HTTP server for Rack applications designed to only serve fast clients on low-latency, high-bandwidth connections and take advantage of features in Unix/Unix-like kernels.
- SimpleCov - SimpleCov is a code coverage analysis tool for Ruby 1.9.
- Zeus - Zeus preloads your Rails app so that your normal development tasks such as console, server, generate, and specs/tests take less than one second.