For Windows Users

This a bit theoretical (untested, please correct me if I am wrong)

If you don't have jruby-1.7.8 installed you can read about the windows installer here, which ideally you should install. Otherwise you will need to have a regular ruby installed (at least version 1.9.3). The windows install relies on you manually supplying jruby-complete(version).jar and the distribution processing(version).zip, these should both be placed in the vendors/windows folder (edit the Rakefile if you are using 64bit version of processing, currently designed to use processing-2.1b1).

Note for the development version you only need to put the jruby-complete in the vendors folder if you haven't got wget installed

Then all you need to do build and install ruby-processing is to cd to ruby-processing