Steve Ballmer announced yesterday at CES that the Windows 7 Beta is available, effective immediately, to MSDN, TechBeta, and TechNet subscribers via downloadable-image. The general public will have access to the Windows 7 Beta, on or after Friday. Here's a link to the CES keynote: http://www.microsoft.com/presspass/events/ces/default.aspx
For those of you who don't have access to MSDN, TechBeta, or Technet, I would suggest that you visit http://www.microsoft.com/windows/windows-7/, and register for the Windows 7 team's RSS feed, so that you can get the latest news on the availability of the public Beta release.
Here's the placeholder link for the public bits: http://msdn.microsoft.com/evalcenter/dd353271