Wikipedia
RadRails
RadRails is a Rapid Application Development IDE for the Ruby on Rails framework. The goal of RadRails is to provide Ruby on Rails developers with everything they need to develop, manage, test and deploy their applications. Features include source control, code assist, refactoring, debugging, WEBrick servers, generator wizards, syntax highlighting, data tools, and much more.
The RadRails IDE is built on the Eclipse RCP, and includes the RDT and Subclipse plug-in. The RadRails tools are also available as Eclipse +plug-ins.
At EclipseCon 2006 RadRails won the Community Award for Best Open-Source Eclipse-based tool.