SharePoint 2010 is starting to appear on MSDN/Technet, etc. And publicly available components are now available for download. Links and info are below:
Microsoft SharePoint Designer 2010
Reminder: SharePoint Designer 2010 only connects to SharePoint 2010 sites. You will want to continue to use SharePoint Designer 2007 to connect to your WSS/MOSS sites. I suggest you stick with 32bit versions of Office so that you can install Designer on your machine (you can’t mix 32bit and 64bit Office versions).
Microsoft SharePoint Foundation 2010