Post Update: You can get the latest Windows Server 2012 Build from this link.
To start using Windows Server 8 (Windows Server 2012) you can download the ISO from the MSDN website. Windows Server 8 Developer Preview is currently available only for those developers who actually subscribe to MSDN and can access and download the Windows Server 8 Developer Preview. However, the Windows 8 Developer Preview Build 8102 Milestone 3 (M3) can be downloaded by all users from the download link given at the end of this post.
Microsoft recently unveiled the new Windows 8 and Windows Server 8 Preview edition to familiarize developers with the upcoming Windows operating system. Windows Server 8 has come with a number of enhancements such as Server Manager options which allow users to add remote servers and to organize them in custom server groups, perform tasks on multiple servers simultaneously, remotely deploy roles and features, and can obtain the current status of associated servers and roles. You can also set a custom refresh rate for gathering required data.