diagrams for your rails apps
RailRoad lets you generate diagrams of your rails app.
Documentation often gets left to get out of date. With a tool such as this, you can just keep changing the code, automatically generating diagrams along the way.
The link above tells you how to set up a rake task to do just this, meaning that you’ll never have to look at a redundant diagram again (or manually update one either)!
I'm Richard Roberts, a developer in the UK working with Ruby on Rails. I'm a founder of: 
