LXC Web Panel

As you (probably) already know, LXC (Linux Containers) or OpenVZ an operating-system-level virtualization is really faster than hardware virtualization, see the comparison. For those who hate CLI, you can use web interface called LXC Web Panel (for LXC 0.7 to 0.9, or newer fork 1.0+ here) to manage your containers:

wget https://lxc-webpanel.github.io/tools/install.sh -O - | sudo bash

This software only works on Ubuntu 12.04 or later. Despite of its performance, of course there are limitations, such as: you can only use host OS and architecture on guest. You can find more info on their website or this blog post.

So why LXC instead of Docker or Virtualization? because it's simpler :3 yes, both are different kind of animal, don't forget to check LXD and other alternatives too.