Feb 2019 Update - I have moved the Handlebar Code into it’s own project and its available as a stand alone module without needing to worry about Sitecore Foundation. You can find the code and installable Sitecore Packages on github here.
One of my favorite features of Sitecore Foundations are Handlebar Components. Using these components you can build UI quickly using existing markup and create variants of UI even quicker. Basically how it works is by binding Handlebar templates managed in Sitecore to a Dynamic Item Wrapper that wraps the Sitecore Item and makes it's fields and properties available.
Here's a video that demonstrates the Airspace Site and how Handlebar Components were used.
I've actually writted some decent documentation on using Handlebar Components in the Github Wiki.