1. Code Markup is an easily customizable plugin that removes most HTML tags so that code can be displayed properly but leaves others in so that the code can be illustrated easily.  The code will, for the most part, be displayed precisely as you type it.
2. Code Snippet is a popular code highlighter plugin and ideal for illustrating portions of code in a variety of different languages.  This plugin is also scalable so if a language you want to illustrate is not supported you can typically add it.
3. For developer sites, the Developer Formatter is a great way to have a robust plugin for a multitude of uses.  Supporting well over one hundred programming languages, this is ideal for the WordPress blog that features code from multiple languages.  PHP, ASP, CSS, HTML and more are among the languages supported.
4. FV Code Highlighter uses a similar format as Dreamweaver to highlight particular types of code so anyone familiar with that coding scheme will have an easy time looking through your coding samples.  It will highlight code from HTML, PHP, CSS and XML.  The highlight colors can be changed if you prefer them something different but the familiarity with Dreamweaver makes the default settings quite useful.
5. WP Advanced Code Editor allows you to create new pages and new posts highlighting code within the WordPress blog.  In addition to a full coding display it also has line numbering.  However, make sure the WYSIWYG editor is disabled when this plugin is in use or it will conflict and not work properly.

All of the plugins are very useful and all work really well.  The differences will depend on the uses you need when you install the plugin.  Each one comes highly recommended and is tested through version 2.5 of WordPress.  However, it is likely that they will all work flawlessly with the latest versions also.

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