First, download and install NXC.
gem install rubotz.
Then fill out the config YAML (it only takes a second).
Next write your program in Ruby, and use the
Rubotz.compilecommand to generate an executable
.rxefile in your NXC
Finally, use a third-party library like NXTBrowser to transfer your executable to your Mindstorms NXT brain.
Boom: robot. Programmed in Ruby.
However please note: Rubotz v0.0.1 is a proof-of-concept developer release only. It currently only supports one sensor, synchronized motor functions, and single-threaded NXC. The full complement of available sensors, motor functionality, and threads should become available in future releases, and if you want to help that happen, go for it.