NetBeans
Netbeans can be downloaded here : http://netbeans.org/
Please check if you distribution embed Netbeans packages.
On Debian/Ubuntu, a simple
$ apt-get install netbeans
will install netbeans.
On Gentoo, use emerge
$ emerge netbeans
To use NetBeans with Rails, install the the Ruby and Rails plugin (from Tools>Plugins).
Please first install Ruby on Rails plugins for Netbeans
In order to use it with MarkUs, choose to create a new Ruby on Rails Application from existing sources
It was not recommended to create a NetBeans project out of the existing MarkUs source. We used it only to edit individual files with. NetBeans used to change the configuration files you have carefully set up already, causing many things to stop working. If this happens, look in particular inside config/database.yml and restore any settings that NetBeans has changed.
New project with existing sources
You can use a différent Ruby Plateform if you wish to
Moreover, Netbeans can embed a Git plugin, to help you with source management.
Netbeans and Git
BE CAREFUL : A graphical user interface for Git doesn't mean you don't have to understand what you do. If you don't use Git properly, you can lose data !