Ruby is a programming language with several implementations. Besides the standard runtime, there is JRuby, which runs on the JVM, and IronPython, which runs on .NET and Mono.
Ruby recommender system resources
- Ruby on Rails contains information about using recommender systems with this web application framework.
- If you use JRuby, you can use Mahout, LensKit, and other libraries implemented on the JVM.
- MyMediaLite can be called from IronPython: http://ismll.de/mymedialite/documentation/use_from_ruby.html
- recommendify  is a recommender based on Ruby and Redis
- Implementing the Pearson correlation algorithm using Ruby and the GNU Scientific Library by Chris Lowis