So, what is Docker and why should we care about a 0.x release? Yes, I looked at the link and no, I was not much the wiser, something to do with virtualization perhaps?
Docker complements LXC with a high-level API which operates at the process level. It runs unix processes with strong guarantees of isolation and repeatability across servers.
Docker is a great building block for automating distributed systems: large-scale web deployments, database clusters, continuous deployment systems, private PaaS, service-oriented architectures, etc.
Maybe, "Docker is a system for creating and deploying self-contained application packages for Linux," except I'm pretty sure "application package" is the wrong phrase. But that's the gist of why it's interesting, IMHO.