RadRails – A Ruby on Rails IDE: Looks interesting. I couldn’t find much in the way of screenshots, though. There’s a video, but it’s about how to import a project, not about actually using the app.
RadRails is an integrated development environment for the Ruby on Rails framework. The goal of this project is to provide Rails developers with everything they need to develop, manage, test and deploy their applications. Features include source control, debugging, WEBrick servers, generator wizards, syntax highlighting, data tools and much much more.
Open source — it’s built on Eclipse, in fact.