Microsoft released the public beta for Office and SharePoint Server 2013.

You can find more information in the following articles:

• Office Customer Preview
• SharePoint, Exchange, Lync, Office Web Apps, Project, Visio, Office Professional 2013 Preview
• Microsoft unveils the new Office
• Webcast: Announcment from Steve Ballmer

Direct links for SharePoint 2013

• SharePoint Foundation 2013 Preview
• Microsoft SharePoint Server 2013 Preview
• IT Pro and Developer training materials
• Technet Material
• More Material