The first beta release of Windows 7 may be out in just over a month, according to the official website of the MSDN Developer Conference. About half-way down the site's about page, you'll see a "Giveaways" section, the Windows 7 logo, and the following text sitting right under it:
All attendees will receive a Windows 7 Beta 1 DVD. Attendees at events scheduled for December will have DVDs mailed to them when they become available.
The first two MSDN Developer Conferences to take place after December are scheduled for January 13, so the note strongly suggests Microsoft will start handing out Windows 7 beta DVDs then.
Microsoft revealed last month that Windows 7 would likely hit stores before the end of next year, so the beta cycle may be shorter than with previous releases. The first Windows XP beta came out almost exactly a year before the OS's launch, and Vista Beta 1 was out in late July 2005, about 18 months before Vista's retail debut.