Copied code style from railscasts.
Need coderay gem installed ahead.

More about CodeRay see: http://coderay.rubychan.de/doc/classes/CodeRay.html

How to use
1.install coderay: 
sudo gem install coderay
2.copy coderay plugin to vendor/plugins
3.Use in rails: 
CoderayString.new(string).format
4.Input code should be like:
[code:ruby]
def hello
  puts "hello world!"
end
[/code]

Exmple see:
http://zhangzhe.heroku.com/blogs/62-code-style-from-railscasts