The pipeline opened for the Windows 7 RC on May 4th. While originally stating that downloads would cease in late July, Microsoft has twice extended it, first to August 15th, and later to August 20th. That would be today, if you're calendar-phobic.
The RC gives you a chance to run Windows 7 for free, at least until next year. Naturally it's not the final software, but by all reports, it's pretty darn stable. Windows 7 RC is set to nagging you on March 1, 2010; it will begin to automatically shut down at two-hour intervals on that date. D-Day is June 1, 2010 after which the OS will not boot at all.
After the Windows Vista fiasco (let's be honest; that's what it was), Microsoft is looking to Windows 7 to re-invigorate its OS division, so to speak, as well as its coffers. Still, many businesses have said they might skip Windows 7, or at least delay adoption, in this time of recession.
Launch date for Windows 7 is Oct. 22nd. Prior to that date, while MSDN members and certain others can obtain an early copy, John Q. Public can obtain a legal copy by attending one of the 25 launch events Microsoft is hosting in the U.S. Those events begin Sept. 24; acomplete list of the sites and schedule is available on Microsoft's site.
Update: It's gone; say goodbye.