YARD
YARD is a Ruby Documentation tool. The Y stands for "Yay!"
With the new dynamic documentation server in YARD 0.6, you can now see exactly what YARD sees as you document your code. Simply type yard server, reload to have your project watch for changes in your codebase everytime you refresh the page. With this functionality, you almost have no excuse not to write documentation! You can write all kinds of extensions in YARD, including ones that can understand all of the dynamic magic your framework does in its own little Domain Specific Languages (DSLs). Most importantly, it's really easy to do! There are already plugins that support frameworks like RSpec, DataMapper, Sinatra, and support for others are in the works. YARD is the only Ruby documentation tool that supports storing metadata alongside your documentation. This metadata can be used to create consistent documentation in any format you wish. YARD also comes with a powerful templating system to quickly modify existing templates.