Sinatra : Classy web-development dressed in a DSL

sinatra.rubyforge.org — The world doesn't think it needs another Ruby web framework, but Sinatra is so different it will cut out a new market. A whole web app can be encapsulated in a single Sinatra file, making it especially ideal for small projects like Facebook apps. It even includes Haml markup! It was born out a need for something lighter than Ruby on Rails.