Celerity is a JRuby wrapper around HtmlUnit – a headless Java browser with JavaScript support. It provides a simple API for programmatic navigation through web applications. Celerity aims at being API compatible with Watir.

HaikuPorts is a centralized collection of software ported to the Haiku platform. Each port contains the Haiku-specific patches to the original source code.
Licenses used remain the same as the original software.

RDF.rb is a pure-Ruby library for working with Resource Description Framework (RDF) data.

Forum, mailing list, chat, weblog all in one, where one can propose, vote and delegate on any element.Security through 3 elements: P2P, pgp signatures, electoral lists.

A platform for developing apps using JRuby on Android.,

Graylog2 is an open source syslog implementation that stores your logs in MongoDB. It consists of a server written in Java that accepts your syslog messages via TCP or UDP and stores it in the database. The second part is a Ruby on Rails web interface that allows you to view the log messages. It also implements GELF. The Graylog Extended Log Format is a simple JSON string that allows you to send long and structured syslog messages and very useful for customized application log monitoring....

sidekiq provides simple and efficient message processing for Ruby applications. It aims to be compatible with Resque where possible to leverage existing code and monitoring tools.

Mxx_ru (Make++ on Ruby) is a cross-platform build tool. It's intended for C/C++ languages in general, but it's easy to extend for handling other languages. It uses a template based approach for describing build process.

Official Ruby Driver for MongoDB,

The Player Project: Player is a networked interface to robots and sensors. Stage and Gazebo are Player-friendly multiple-robot simulators. The software aims for POSIX compliance and runs on most UNIX-like OS's. Some parts also work on Windows.