If a PaaS/VPS provider is actually USING Docker to provide their service, it probably wouldn't be the best platform to actually TRY Docker in. It's easy enough to get it set up on DigitalOcean; I created a tutorial at https://www.digitalocean.com/community/articles/how-to-insta...
Actually my second sentence was not connected to the first. I was curious if there are any PaaS providers using Docker as the underlying infrastructure. And I also would like to setup openstack-docker and play around with it (not inside a PaaS or VPS of course). I did see your tutorials though, definitely another great way to test out Docker quickly.