Microsoft appears to have accidentally pulled the trigger on a blog post announcing the new Windows 8 Release Preview. The post was dated today, May 31st, but actually posted yesterday afternoon. It was quickly removed.
The post originally went up on the Windows Hardware and Driver Developer Blog. It was taken down shortly after posting, but not before The Next Web managed to get a screenshot. It was written by Chuck Chan, the Corporate Vice President for the Windows Development Team. It provided download links for the Windows 8 Release Preview, the Windows Driver Kit 8, and Visual Studio Professional 2012 (which includes the Windows 8 SDK).
Of course, since the post was actually dated today, it should be going back up again at some point soon. Which, of course, means that the Windows 8 Release Preview should be available for download later today. There's no indication of when Windows 8 itself might release, though the post promises weekly or bi-weekly posts until it does.