Toying with Vagrant without autocomplete is definitely not much fun as just for listing all the VMs you would have to type
vagrant global-status (I know you can use the help menu or create aliases but I just prefer autocomplete).
$ sudo wget https://raw.github.com/kura/vagrant-bash-completion/master/etc/bash_completion.d/vagrant -O /opt/local/share/bash-completion/completions/vagrant
then add the following lines to your
if [ -f /opt/local/etc/bash_completion ]; then . /opt/local/etc/bash_completion fi