Stephen Harris

This plugin allows you to write posts (of any post type) using the Markdown syntax. The plugin converts the Markdown into HTML prior to saving the post. When editing a post, the plugin converts it back into Markdown syntax.
The plugin also allows you to enable Markdown in comments and bbPress forums. In these instances the plugin adds a toolbar, and preview of the processed Markdown with <a href="http://code.google.com/p/google-code-prettify/" rel="nofollow ugc">Prettify</a> syntax highlighter applied (similiar to that used in the Stack Exchange websites such as <a href="http://wordpress.stackexchange.com/" rel="nofollow ugc">WordPress Stack Exchange</a>).
WP-Markdown stores the processed HTML, so deactivating the plugin will not affect your posts, comments or bbPress forums.

WP-Markdown

Version 1.5.1 of the plugin works almost perfectly.
I'm just waiting for the upcoming 1.6 update (which is in alpha on GitHub) to be pushed, so I can use GitHub Flavor-style codeblocks specifying the exact language.



Waiting for 1.6

Allows Markdown to be enabled in posts, comments and bbPress forums.

a454213722

This plugin code prettify plugin using google code prettify.This plugin highlighting of code snippets in your post for WordPress Blog. | 在你博客文章中使用Google Code Prettify美化代码，很酷的代码高亮插件
Related Links: 
* <a href="http://www.phpsong.com" rel="nofollow ugc">Plugin Homepage</a> 
* <a href="http://code.google.com/p/google-code-prettify/" rel="nofollow ugc">Google Code Prettify</a>
<h3>Translations</h3>
此插件支持目前只支持中文。

WP-code-button

This plugin code prettify plugin using google code prettify. the code higlighting effect will be seen directly in the tinymce editor.

WP-Markdown vs WP-code-button