For my website I created a wrapper of Syntax Highlighter by Alex Gorbatchev. Its a simple plugin that allows you to add Syntax Highlighting to a block of code in wordpress. Can look at any other of my Code Samples to see it actually work. Its a quick thing I did this morning, so there is room for improvement.
To get it to work just need to enclose any code in [code] shorttags. You can specify which language you wish to highlight and there are options for applescript, as3, bash, coldfusion, cpp, csharp, css, delphi, diff, erlang, groovy, java, javafx, jscript, perl, php, plain, powershell, python, ruby, sass, scala, sql, vb, and xml.
The plugin itself can be downloaded at http://www.nicholeboseman.com/wp-content/uploads/codeblock.zip. It still has a lot of work that needs to be done but as you can see it gets the basic job done.