This is a fork and modification of https://github.com/coreos/coreos-vagrant, credit goes to CoreOS for the real work
Just run vagrant up and the UI/API will be available at port 9080.
Copy vagrant/config.rb.sample to vagrant/config.rb and then change num_instances.
Then go to https://discovery.etcd.io/new and get a new token to put in vagrant/user-data.