By default Sitecore comes with a sample site that is built on web forms and XSLT. This repository contains MVC versions of the code for the out-of-the-box Sitecore sample site.
The code in this repository is explained in detail on my blog.
This repository is available as a Sitecore package under Releases. When installing the package, you will be prompted Item being installed already exists in database. Choose the Overwrite option and click Apply to all. Perform a full site publish after installing the package.