Update: 2019-03-11
First of all thanks for those who have upvoted this answer over the years.
Please be aware that this question was asked in August 2013, when Docker was still a very new technology. Since then: Kubernetes was launched on June 2014, Docker swarm was integrated into the Docker engine in Feb 2015, Amazon launched it’s container solution, ECS, in April 2015 and Google launched GKE in August 2015. It’s fair to say the production container landscape has changed substantially.
The short answer is that you’d have to write your own logic to do this.
I would expect this kind of feature to emerge from the following projects, built on top of docker, and designed to support applications in production:
Update 1
Another related project I recently discovered:
Update 2
The latest release Openstack contains support for managing Docker containers:
Update 3
System for managing Docker instances
And a presentation on how to use tools like Packer, Docker and Serf to deliver an immutable server infrastructure pattern
Update 4
A neat article on how to wire together docker containers using serf:
Update 5
Run Docker on Mesos using the Marathon framework
Mesosphere Docker Developer Tutorial
Update 6
Run Docker on Tsuru as it supports docker-cluster and segregated scheduler deploy
Update 7
Docker-based environments orchestration
Update 8
Update 9
Google kubernetes
Update 10
Redhat have refactored their openshift PAAS to integrate Docker
Update 11
A Docker NodeJS lib wrapping the Docker command line and managing it from a json file.
Update 12
Amazon’s new container service enables scaling in the cluster.
Update 13
Strictly speaking Flocker does not “scale” applications, but it is designed to fufil a related function of making stateful containers (running databases services?) portable across multiple docker hosts:
Update 14
A project to create portable templates that describe Docker applications:
Update 15
The Docker project is now addressing orchestration natively (See announcement)
Update 16
See also:
Update 17
The Openstack project now has a new “container as a service” project called Magnum:
Shows a lot of promise, enables the easy setup of Docker orchestration frameworks like Kubernetes and Docker swarm.
Update 18
Rancher is a project that is maturing rapidly
Nice UI and strong focus on hyrbrid Docker infrastructures
Update 19
The Lattice project is an offshoot of Cloud Foundry for managing container clusters.
Update 20
Docker recently bought Tutum:
Update 21
Package manager for applications deployed on Kubernetes.
Update 22
Vamp is an open source and self-hosted platform for managing (micro)service oriented architectures that rely on container technology.
Update 23
A Distributed, Highly Available, Datacenter-Aware Scheduler
From the guys that gave us Vagrant and other powerful tools.
Update 24
Container hosting solution for AWS, open source and based on Kubernetes
Update 25
Apache Mesos based container hosted located in Germany
https://sloppy.io/features/#features
And Docker Inc. also provide a container hosting service called Docker cloud
Update 26
Jelastic is a hosted PAAS service that scales containers automatically.