Geoffrey Grosenbach is the host of the acclaimed Ruby on Rails Podcast. His Gruff graphing library for Ruby is in wide use even though it has not convinced the Ruby elite that he is a legitimate Rubyist. He’s working on that by donating large sums of cash to the Seattle.rb which will be used to fly in noteworthy Rubyists to lecture in Seattle over the coming year.
You can read about some of his open source projects in the essential Ruby Cookbook.
He teaches Ruby on Rails workshops all over the world with Carson Workshops. You can keep up on his current endeavors and Rails epiphanies at his blog, Nuby on Rails or contact him via the Topfunky Corporation.