Now ultraviolet is easy to use on RoR thanks to Jeremy McAnally, which has just released Radiograph:

"Radiograph is a small Rails plugin to expose Ultraviolet (http://ultraviolet.rubyforge.org/) to Rails views. Ultraviolet is a syntax highlighting library which makes use of Textpow which parses Textmate bundles (whew!). This plugin lets you use Ultraviolet’s syntax highlighting capabilities in Rails applications. It parses a Textmate syntax and generates HTML based on a Textmate theme."

Plugin page:

http://agilewebdevelopment.com/plugins/radiograph

Repository:

http://code.jeremymcanally.com/radiograph