Update: Google has made changes to their verification process and wordpress.com has a new method for verifying blog ownership with Google, Yahoo and Bing.  WordPress.com makes search engine verification easy

Courtesy of Tigre de Fogo
Tutorial: How to make Google verify your WordPress.com Blog (Verify site ownership)

Google Webmaster Tools
“Our suite of webmaster tools provides you with a free and easy way to make your site more Google-friendly. They can show you Google’s view of your site, help you diagnose problems, and let you share info with us to help improve your site’s visibility. … The first step to increasing your site’s visibility on Google is learning how our robots crawl and index your site. … A second step is learning what drives traffic to your site.”

Reference: Google Site Verification and Site Map