SyntaxHighlighter Evolved

I needed a plugin to display example code in WordPress. This is a good article with about a dozen of these plugins:

15 WordPress Plugins for Displaying Code Snippets

SyntaxHighlighter Evolved allows you to easily post syntax-highlighted code to your site without losing it’s formatting or making any manual changes. It uses the SyntaxHighlighter JavaScript package by Alex Gorbatchev.

For a live demo, see this plugin’s homepage.