There has been much rumour that Matt Cutts, software engineer at Google, is the infamous GoogleGuy of the WebmasterWorld forums. Whether these rumours are true or not he is definitely an authority on all things Google.
The good news of the day is that Matt has recently started a blog on Google and SEO (with a few other webmaster tips tossed in). This blog is definitely one to watch as a Google software engineer gives tips on how to optimize your site.
Definitely a page to add to your favorites and visit regularly, you can view it at http://www.mattcutts.com/blog/.