As you already may know, YaST is the administrative control panel from OpenSUSE and SUSE Linux. It has both a GUI, implemented with GTK and QT and a command line interface, for the servers without any graphical environment.
YaST is a very powerful tool, used for installing packages, user management, creating or resizing partitions and many other tasks.
The new YaST, rewritten in Ruby will be available on openSUSE 13.1, which will be released at the beginning of August.
Ruby is a simple and flexible programming language, so the redeveloping of YaST will be done rapidly.