Also known as @tenderlove, Aaron did change the parsers arena in the Ruby world with his contributions on open source projects such as Psych, the new Ruby 1.9 YAML parser. Moreover, if you deal with XML nowadays, chances are that you’re using Nokogiri underneath. Before that we only had REXML and Hpricot, but Nokogiri delivered on performance. Another project was Mechanize. Because of that we now have great parsers for the main internet formats, specially if you consider that in Rails the JSON parser is actually the YAML parser.
Also known as @seacreature and also known for Ruby Mendicant. I was used to use his Ruport project before, which leverages the ancient PDF Writer to generate PDF reports. But PDF Writer was abandoned. So Gregory decided to create a new foundation to deal with PDF and from there we got Prawn, a more modern and capable Ruby library. Besides that he authored the “Ruby Best Practices” book, which I recommend to anyone interested in improving their skills with Ruby.
Also known as @qrush, he is young and works for Thoughtbot, the company that brought to us lots of great open source projects such as Paperclip or Shoulda. But Nick had a complain: publishing gems was a tedious process through the good old RubyForge.net.
Github radically changed the process of working with open source, but in order to publish the gem packages we still had to cope with the old way. So Nick created Gemcutter.org, which evolved rapidly and ended up taking the place of Rubygems.org, becoming the de facto gem repository. So Github + Gemcutter modernized our open source process.
Wayne E. Seguin
This is easy: @wayneeseguin. Wayne became well known because of his most recente project, the RVM. It is now possible to have many different versions and different Ruby implementations running side by side in the same environment. We can have Ruby 1.8 and 1.9 and JRuby running along. Even better: we can configure each project with its onw particular Ruby implementation. A simple “rvm ruby-1.9.2” command is enough to hot swap environments. This changed our way of organizing our projects, making it an order of magnitude easier. Moreover, made it easy to have multiple web apps that depend on different Ruby settings, all running side by side in the same web server. Literally worth the award.