The Dec 2006 CTP of WPF/E is now available for download.  If you're interested in this, you'll want to check out the following links:

• Download the Windows CTP at http://go.microsoft.com/fwlink/?LinkID=77792&clcid=0x409 and the Macintosh version at http://go.microsoft.com/fwlink/?LinkID=77793&clcid=0x409
• There is an SDK available at http://go.microsoft.com/fwlink/?LinkID=77791&clcid=0x409
• In normal Microsoft fashion, the docs are also available online at http://msdn2.microsoft.com/en-us/library/bb188266.aspx and there is a forum at http://forums.microsoft.com/MSDN/ShowForum.aspx?ForumID=1182&SiteID=1, which is currently very empty
• The MSDN developer center is at http://msdn.microsoft.com/wpfe
• There are samples on Mike Harsh's blog, as well as here, here and here.
• There is another interesting blog at http://blogs.msdn.com/webnext

And lastly, you can always check my own summary of what WPF/E has to offer (written pre-release).

UPDATE: WPF/E is now better known as Silverlight.  An unusual example of Microsoft changing from a clunky codename to a cool product name!