If you are a MSDN subscriber, you can download Windows 7 Beta right now.

Please connect to the download web site and use your credentials.

Windows 7 beta is here .... waiting for you

/* Update : Jan 9th
If you are not an MSDN subscriber, the beta will be available for download today on http://www.microsoft.com/windows/windows-7/default.aspx (Friday 9th - US time)
only 2.5 million downloads available, so don't wait :)
thank you */

J.