After having received a comment from Steven Ross I saw in his website a reference to RadRails.

I must say that I have never used Eclipse before, but this application literally blew my mind. I had known it before doing the application I’ve blogged about before! I strongly recommend it: ruby code highlighting, integration with Subversion, available for Mac, Linux and Windows, data manipulation screens, and under strong development. The first version is dated October 2005 and apparently is getting lots of contributions; the current version is 0.5.1 and it is stable enough for everyday use.

Thanks Steven for the reference!