I use Apple's Keynote for doing my presentations and naturally these include some bits of code that need highlighting so that it's easier to read. [...] In the end I used GESHI which is a highlight library written in PHP that supports the syntax highlighting of around 50 different programming and scripting languages.

He's provided his sample implementation to help you get up and running. You'll need to download and install GESHI to get it working though. Here's an example of the output.

What if I told you that with as little as 3 lines of code, you could highlight code on your site? You'd jump at it, wouldn't you? Why not run with the big boys? Your users will love you for it and for good reason. It greatly increases readability.

He walks through the simple installation and how to use it in your page - complete with the code he uses to include the functionality in your page.