Ruby/Graphviz provides an interface to layout and generate images of directed graphs in a variety of formats (PostScript, PNG, etc.) using GraphViz.
Ruby-Processing is a ruby wrapper for the processing-2.0 art framework. This version supports processing-2.2.1, and uses jruby-complete-1.7.26 or an installed jruby as the glue between ruby and java. Use both processing libraries and ruby gems in your sketches. The "watch" mode, provides a nice REPL-ish way to work on your processing sketches. Features a polyglot maven build, opening the way to use/test latest jruby.