It looks like RadRails, the Eclipse-based IDE that has become quite popular, has shut down completely. The codebase is to be incorprated by Aptana for inclusion in their open-source web development IDE, but it’s not apparent when that will be. As of today, radrails.org is now offline meaning that getting a copy of the software is much harder.
Those missing the plugin repository should be using the one by Ben Curtis at www.agilewebdevelopment.com/plugins.
Don’t hesitate to use Eclipse for Rails if you need a good replacement, or use the article that started it all to build your own environment. My upcoming book will recommend that in place of RadRails and will also mention several other free and commercial Rails IDEs.
I look forward to Aptana working on this project, as I believe they have the ability to make RadRails work the way it should work. I never used RadRails, nor have I ever recommended it to any clients, friends, or coworkers, but I do wish the RadRails team the best of luck in their new endeavors.