Hello

The SharePoint Server 2013 Preview is available to download from the next page:

http://technet.microsoft.com/en-us/evalcenter/hh973397

On the other hand, it has been also release some content for IT-Pros and developers

IT-Pros

http://technet.microsoft.com/en-US/sharepoint/fp123606

http://www.microsoft.com/en-us/download/details.aspx?id=30361

Developers

http://msdn.microsoft.com/en-US/sharepoint/fp123633

http://msdn.microsoft.com/en-us/sharepoint

I would like also to point you to the next page for more info:

http://sharepoint.microsoft.com/en-us/preview/sharepoint.aspx   

Thanks.

Kind Regards.

Héctor Calvarro Martín. SharePoint Dev/Core. Microsoft Support Escalation Engineer for EMEA