Wordpress PHP Exec Plugin
This plugin lets you execute dynamic PHP code in posts. It masks PHP code before balanceTags, and unmask them afterwards, so it should be safe to use PHP code that has literal HTML tags in it, for example: code which print out HTML.
Requirement
WordPress 1.5. Version 1.2 is not supported. You will also need PHP version 4.3.0 or later.
PHPExec