Drupal - Submit Again

Add a second button to the form, make sure there is an additional submit function included:

$form['buttons']['submit_again'] = array(
    '#type' => 'submit'
    ,'#value' => t('Save and create another')
    ,'#weight' => 41
    ,'#submit' => array('node_form_submit', 'submitagain_node_form_submit')
);
$form['buttons']['submit_again'] = array(
    '#type' => 'submit'
    ,'#value' => t('Save and create another')
    ,'#weight' => 41
    ,'#submit' => array('node_form_submit', 'submitagain_node_form_submit')
);

After that, it's a simple matter of using the extra function for routing purposes:

function submitagain*node_form_submit($form, &$form_state) {
    $form_state['redirect'] = 'node/add/'. str_replace('*', '-', \$node->type);
}
function submitagain*node_form_submit($form, &$form_state) {
    $form_state['redirect'] = 'node/add/'. str_replace('*', '-', \$node->type);
}