Ruby In Steel provides debugging for Rails applications in addition to ‘pure Ruby’ programs. The Developer Edition features two debuggers – the fast 'Cylon' debugger and the slower Ruby debugger. The simplest way to start a Rails debugging session is by clicking the 'One-Click Rails Debugger' button on the Ruby Toolbar. Alternatively, you can debug applications by loading and running the Server file of your application.
See Also
Ruby On Rails Debugging
Debugging Rails Via The Server Script
Tutorials
Debugging Rails With WEBrick
Debugging Rails With Cylon
Debugging
The Debugger
Tools
Ruby and Rails Tools