During its development, Windows 8 has gone through different stages. The current stage is Consumer Prieview which is a beta stage (Febuary 29, 2012).
The next stages include Release Candidate (April 2012) and RTM (which if production stays on track is said to be released in August 2012).
Microsoft info link:
http://windows.microsoft.com/en-US/windows-8/iso
http://live.theverge.com/Event/Microsofts_Windows_8_Consumer_Preview_event_at_MWC_2012?Page=0
Download link
x64bit :
http://iso.esd.microsoft.com/WCPDL/BD1B8A49393E30CC9C4E5C88457D73E964F1F3B18/Windows8-ConsumerPreview-64bit-English.iso
x32bit :
http://iso.esd.microsoft.com/WCPDL/BD1B8A49393E30CC9C4E5C88457D73E964F1F3B18/Windows8-ConsumerPreview-32bit-English.iso
