John

This plugin enables you to highlight syntax using the PEAR Text_Highlighter class. Other syntax highlighters that use GeSHi have slower rendering speeds which will increase your page load time. However, this plugin gives you the speed and efficiency provided by the PEAR developers. You even have the option of enabling or disabling the line numbers as well as specifying your own style.

Ion Snytax Highlighter

This plugin allows users to highlight code.

zeaks

A simple code snippet plugin for anyone who wants to post any type of code on their site. It’s what I’ve used on Zeaks.org for a while, and highly based off of Danny Van Kooten’s Simple Quote Code Snippets plugin. It’s lightweight, uses no JavaScript, comes with 4 editable color schemes and very easy to use.
Note Does not highlight code, simply displays it in a nice way and allows posting of any code.
Use [code] Your Code [/code] in any post.

Zeaks Snippets

A simple, lightweight code snippet plugin with 4 color schemes that displays code in posts similar to how Wordpress.org does.

Ion Snytax Highlighter vs Zeaks Snippets