Those of you who publish small websites know we live or die at Google's whim, so it's always news when Google releases new information regarding publisher best-practices.
The problem in the past has always been Google's ambiguity. Google doesn't want to give so-called Black Hat publishers information they can use to trick Google and game the system. But that same ambiguity makes it much harder for those who play by the rules to stay in compliance. After all, if you don't know what the rules are, it's awfully hard to obey them.
Google Anti-Spam Guru Matt Cutts talks about the new documentation on his blog: Improved SEO Documentation Galore! The info is thankfully quite explicit (at least for Google), and offers numerous useful tips for publishers. If you're got a website, it's must-read stuff. Even if you're not a web publisher, if you've even been curious as to some of the workings behind the curtain at the massive Google machine, I think you'll find it interesting.