[BSchwarz]

That's right. Windows 8 client and server are now available for download. The downloads are developer preview builds and come in both x86 and x64. There are 2 version of Windows 8 you can download. One with developer tools and one without.

There is no upgrade path so a clean install is required. Follow the links below to grab the copy of Windows 8 that you prefer. These are direct download links to the Windows 8 ISO.

Windows 8 Developer Preview with developer tools English, 64-bit (x64) (4.8GB)

Sha 1 hash - 6FE9352FB59F6D0789AF35D1001BD4E4E81E42AF

• 64-bit Windows Developer Preview
  
• Windows SDK for Metro style apps
  
• Microsoft Visual Studio 11 Express for Windows Developer Preview
  
• Microsoft Expression Blend 5 Developer Preview
  
• 28 Metro style apps including the BUILD Conference app

Windows 8 Developer Preview English, 64-bit (x64) (3.6GB)

Sha 1 hash – 79DBF235FD49F5C1C8F8C04E24BDE6E1D04DA1E9
Includes a disk image file (.iso) to install the Windows Developer Preview and Metro style apps on a 64-bit PC.

Windows 8 Developer Preview English, 32-bit (x86) (2.8GB)

Sha 1 hash - 4E0698BBABE01ED27582C9FC16AD21C4422913CC
Includes a disk image file (.iso) to install the Windows Developer Preview and Metro style apps on a 32-bit PC.

These builds can be installed on the same hardware that Vista and Windows 7 can be installed on.

[keepitcoder]

Where can I download the server versions?

[BSchwarz]

It's all in the same ISO. On install just choose server. Make sure you download the version with the developer tools.