Check it out - http://go.microsoft.com/fwlink/?LinkId=69434.
I'm really excited about this, as I have been working on some of this content for more than a year. It's great to see that it is publicly available.
Even if you don't have access to Exchange 2007, the content is still very valuable as a learning tool. For example, there is a glossary to get you up-to-speed on Exchange terminology, a great discussion of high availability, best practices for deployment, an extensive technical reference, and much more.
And when you're done reading each page, feel free to use the Feedback control on the bottom of each page to give us your rating and comments. We review every piece of feedback that is sent to us, so if you have an idea, suggestion, correction, or comment, don't be shy! We'd love to hear it.