One of the projects Jumpstart Lab is doing with the Hungry Academy classes is called "StoreEngine." It's a Rails-based ecommerce site. I'm going to build it out using domain objects first, and add Rails at the end, to demonstrate the effects it has on the end system.
The spec: tutorials.jumpstartlab.com/projects/store_engine.html
The repo: github.com/JumpstartLab/store_engine/tree/domain-first