[yock]

RadRails and Redmine are going to be the closest to the Netbeans Ruby support, others have mentioned those already. Something closer to the heart of many Ruby developers is Redcar. It's a text editor installed as a Ruby gem generally meant to replicate Textmate functionality.

http://redcareditor.com/

[messel]

I'd love to see a cross platform variant, influenced by TextMate's design. I tried out redcar last year but it wasn't ready for primetime then. I may be confusing redcar with one of many other editors I tried out last year, I'll give it another look.

update it was redcar that I used last year, and it has improved quickly (kudos to the project team). That's a great sign. Kinda psyched to have something textmate-ish on ubuntu! The themes are pretty hot, and the bundles are chock full of languages.