I know this doesn't answer your question for the CMS-solution but on the current roadshow they did a demo for an EPiServer ECommerce "Reference" site that they will be released in a month or two. They were honest saying that the other Template-sites that they have out now aren't any "Reference"/"Best practice" sites. This new Reference site will first be released on Github and thereafter as a template in the EPiServer extension for Visual Studio, just like the Alloy template (but only for MVC).
Mayby someone else can fill in if I got anything wrong.
As far as I know - not in written form yet. Any particular topic you are interested in?
Frederik Vig's old "Site From Scratch" series was a great introduction:
Someone should write an official guide in that manor for EPi8.
Wow, rekindle an old post for shameless plug, nice
Are there any official best pratices for developing EPiServer CMS solutions defined anywhere?