nginx-proxy sets up a container running nginx and docker-gen. docker-gen generate reverse proxy configs for nginx and reloads nginx when containers they are started and stopped.
See Automated Nginx Reverse Proxy for Docker for why you might want to use this.
To run it:
$ docker run -d -p 80:80 -v /var/run/docker.sock:/tmp/docker.sock -t jwilder/nginx-proxy
Then start any containers you want proxied with an env var VIRTUAL_HOST=subdomain.youdomain.com
$ docker run -e VIRTUAL_HOST=foo.bar.com -t ...
Provided your DNS is setup to forward foo.bar.com to the a host running nginx-proxy, the request will be routed to a container with the VIRTUAL_HOST env var set.
If your container exposes multiple ports, nginx-proxy will default to the service running on port 80. If you need to specify a different port, you can set a VIRTUAL_PORT env var to select a different one. If your container only exposes one port and it has a VIRTUAL_HOST env var set, that port will be selected.