Want to run Ruby on Linux? Follow the instructions in this article to write your first application. It couldn't be easier.
Ruby on Rails is an open source freely available web development framework. It's been quite popular--it won a Jolt "Web Development Tools" award last year, and some prominent Java developers have publically switched to Ruby on Rails. The buzz surrounding Rails is quite impressive--particularly when you consider that Rails had no Fortune 500 company to market it, unlike .NET or Java.
Rails is a Model View Controller (MVC) framework. As you can imagine from the name, applications written using Model View Controller frameworks have three main components: a model, which represents the data and associated logic; the view, which represents how a user interacts with the application; and the controller, which contains all of the business logic that drives the application. This is an artificial distinction, of course, but it is a powerful one.
You'll need Apache 2.0+ and MySQL installed on your Red Hat Linux computer to run these examples.