Justin Williams has a good primer on Ruby on Rails (AKA 'RoR') called 'Ruby on Rails for the Rest of Us'. RoR is a "rapid development framework" for creating online applications. It's generated a lot of interest recently because it's a handy way to develop database-driven sites.
(I was surprised to find out that Twitter of all things runs on it.)
In any case, the article also provides a number of links for further information including the main RoR site, rubyonrails.com
For a taste of Ruby, the programming language that RoR is built on, have a look at 'Try Ruby!"
