CodeRay

I've know coderay since before it's first release and one might laugh knowing that it has it's very roots in a prove of concept that it is possible to write a popper syntax highlighter with nothing but regular expressions.

Of cause since then it has grown a good bad, murphy has done an incredible job in providing a first class interface for Ruby that makes it quite esay to include syntax highlighting in one's Ruby projects without sacrificing performance.

The shipped highlighters are some of the best I've seen and at times are more correct then what is seen in some IDE's. It is also easy to register own highlighters by simply writing a plugin for coderay without getting in every detail of the process.

In addition to that the library comes with a useful CLI that allows quickly highlighting some source to html or other formats for publishing.

So my two cents, if you are looking for highlighting code in ruby, this is what you are looking for.