The PixoPoint Google Docs plugin for WordPress is still in development. It adds a shortcode for embedding Google Docs into your site. The first 40 characters of the URL string in the embed code is checked against a white list of known Google Docs URL strings, then the whole string is parsed through a security filter to ensure that no evil code is injected into the site. This plugin is ideal for use on WordPress multisite networks where non-trusted users may need to embed Google Docs.
Support for automagically converting raw embed code in posts/pages into WordPress shortcodes may be added at some point if there is sufficient demand.