The Sharepoint 2013 ‘Preview’ is out now.
I didn’t see it on MSDN yet, so here is the link:
http://technet.microsoft.com/en-US/evalcenter/hh973397.aspx?wt.mc_id=TEC_121_1_4

Also there’s some training available as well:
Developer training: http://msdn.microsoft.com/en-US/office/apps/fp123626
IT Pro Training: http://technet.microsoft.com/en-US/sharepoint/fp123606