This just in: The Windows 8 client consumer preview (aka, beta build 8250) is officially available here:
Also, the Windows 8 Server beta is also available on TechNet if you are a subscriber. Even if you are not a subscriber, you’ll also want to check out What’s New In Windows Server “8″.
Once you’ve installed the Windows 8 preview you will probably want to install the Remote Server Administration Tools (RSAT) that is compatible with Windows 8.
If you’re evaluating Windows 8 client or server for your business, you probably will also want to check out the Windows 8 Consumer Preview Product Guide for Business.
Here’s Steven Sinofsky’s blog post on the Windows 8 preview system requirements and the official announcement from the Building Windows 8 team.
If you’re interested in writing some new apps to take advantage of Windows 8 and Metro, try the new Visual Studio 11 beta.