There is a rather cool little library that I think should be more widely used: The Syntax Highlighter from Alex Gorbatchev. ( https://github.com/alexgorbatchev/SyntaxHighlighter )
It helps when you want to include little snippets of code, xml, html, php, java, shell, whatever in your web pages. There is a separate Drupal module ( http://drupal.org/project/syntaxhighlighter ) which makes it very easy to use.
Here is an example from their demo page...It is an example of an html page.