I think the author goes in the wrong direction with the list. The other lists (PHP,Ruby,node.js etc) all point to interested libraries and frameworks that can help you developing an application. I expected something like devise (user account management), friendly_id (obfuscating ids).

His list lists applications written in Rails.

That said via three clicks in his github account I found https://github.com/dreikanter/ruby-bookmarks which has an excellent list of gems (libraries, frameworks) so I found what I'm looking for and I'm glad I saw this submission.

Floorplanner

Metasploit

Heroku