It has been mentioned in several places already (e.g. in Denali & CTP3)
but I think it is interesting enough to be mentioned again: The Microsoft® SQL Server® code name 'Denali', Community Technology Preview 3 (CTP 3) Product Guide.
It is a 457MB zip file filled with datasheets, white-papers, examples and demo code with the purpose of helping you to evaluate the next SQL Server version.
So if you are ready to dive into the new features of SQL Server 2012 (This name is not official... yet), this package is definitely a good place to start.
After you unzip the package open the .\SCO1\AltCourse.htm file in the browser of your choice.
From here you can use the menu to click your way through the different topics.
(You can also open the recommended .\SCO1\Course.htm in IE, but it uses a silverlight navigation system that seems more confusing than helpful, at least at first.)