We're building a Win8 FAQ.
News items are in reverse chronological order (newest on top).
Aug. 1, 2012: Win8 has been released to manufacturing. This is commonly known as "RTM" and it basically means that this version of the OS is complete. According to Ars Technica, it will become available to various customers on the following dates:
Aug. 15 to MSDN and Technet subscribers
Aug. 16 to Software Assurance customers and MS Partners
Aug. 20 to MS Action Pack subscribers
Sept. 1 to Volume License customers (who are not on Software Assurance plans)
Oct. 26 in retail stores and on new PCs.
July 18, 2012: MS has announced that Win8 will go on sale October 26, 2012. This is known as the "GA" release date. We didn't previously note it here, but Win8 will "release to manufacturers" (RTM) in the first week of August.
Feb 4, 2012: A little beta fish told me: keep an eye on this page for coming Win8 beta releases.
Dec 2, 2011: Rumor has it that the Win8 public beta will be available in February of 2012
June 1, 2011: MS unveiled Win8 at the D9 conference.They followed with a YouTube video where Jensen Harris previews some of the coming features. The same day, Mike Angiulo did a Win8 demo at the Taiwan Computex 2011. Additionally here is the June 1 press release.