We’ve launched a new site that hosts 30 database entity relationship diagrams for tables of Microsoft Dynamics AX 2012 R2: AxERD.
Check it out here: http://www.microsoft.com/dynamics/ax/erd/ax2012r2/
Check out the introductory blog post here: http://blogs.msdn.com/b/x/archive/2013/05/23/announcing-the-axerd-website-for-dynamics-ax-2012.aspx