Sinatra
Classy web-development dressed in a DSL
Sinatra is a DSL (Domain Specific Language) for quickly creating web applications in Ruby with minimal effort. It is lightweight compared to full MVC frameworks; you define routes (HTTP method + URL pattern) and blocks that handle requests. It leverages Rack for middleware, supports rendering via templates, static file serving, filtering (before/after), helpers, error handling, etc. It's often used for small to medium web services, APIs, and micro-apps.