Welcome to RubyGems.org, the Ruby community's gem hosting service. The purpose of this project is three-fold:
The project was started in April 2009 by Nick Quaranto, and has since grown to include the contributions of over 115 Rubyists and millions of gem downloads. As of the RubyGems 1.3.6 release, the site has been renamed to RubyGems.org from Gemcutter to solidify the site's central role in the Ruby community.
Although Gemcutter is not run by one specific company, plenty have helped us out so far. The current design of the site was sponsored by Thoughtbot. GitHub has also been invaluable for helping us collaborate and share code easily. The site started on Heroku, whose great service helped prove Gemcutter as a viable solution that the whole community could rely on.
Some insights into the technical aspects of the site: It's 100% Ruby. The main site is a Rails application, and the RubyGem serving is done through Sinatra. Gems are hosted on Amazon S3, and the time between publishing a new gem and having it ready for installation is minimal. For more info, please check out the code, which is MIT licensed over at GitHub.