LXC - Linux Containers
Software suites around liblxc
Liblxc is designed to be very flexible, and comes with some basic tools for creating, cloning, and managing containers. Many people have written their own management layers using the liblxc commands (perhaps some using the libraries?) to suit their specific needs and usage preferences. Please feel free to add your own here.
lxc-ubuntu-x - focuses on flexible container generation based on existing containers and templates.
lxc - Just called lxc, this suite allows creating, starting and stopping (Ubuntu) containers and running commands in containers without ssh.