My new article, titled "Google Your Site for Security Vulerabilities" is available here. It includes google_vulns.php, a sample PHP script, which uses the Google API to search for sensitive data.
My new article, Installing and Configuring Nessus, is now available. Part 2 of this article will discuss NASL and how to write Nessus plug-ins. It should be up in a few weeks or so.