Allow me to introduce - SyntaxTranslator. This small script-pack allows you to print PHP and HTML code in better way than just plain text.
With straight code and CSS styles SyntaxTranslator becomes easy-to-use and really flexible script ^_^
Aeperio is a very fast and very flexible syntax highlighter. The script is webbased and can be used for forums, blogs or other sites. You can even create your own language to be highlighted, if you are not satisfied with the provided languages.