We have recently replaced our public demo sites with a great test drive experience, that provides you with your own guided tour through both CMS and commerce. It can be found and started directly on Microsoft AppSource.
It's also worth noting that Episerver's Visual Studio Integration comes prepacked with the Alloy site that is a good reference architecture - and can be used as a demo site.
To access some of our older demo sites, like Qjet or the full Alloy Demo Kit, contact Episerver and request a demo.
You are still able to try our basic Find developer demo, available here: Find Demo (Basic functionality demo for developers with code samples)
Quicksilver reference architecture (download/install from GitHub)