Yeti is an opensource live programming environment for Rhino. Version 0.2 is out at yeti3d.com
This is a tutorial for Yeti based on Axel Kilian's old GC tutorial: generativecomponents.wikispaces.com/roof
With the latest version of Yeti you can reference parameters inside of parameters (eg. *line.start.x) the way object are created is also improved, allowing you to generate arrays of arrays.