Submit Again can re-route users immediately back to node/add/xxx pages after they have submitted a node. It can be turned on for each content type and is off by default. It includes a theme function to control whether or not a status message is displayed to alert users of the location of their recently submitted posts.
This module is useful if you or your users repeatedly submit content, and would like to speed up the process. To use it, activate it on each one of the Content type administration pages you want to have a submit again button (Administer - Content management - Content types - (edit each content type))
For Drupal 7 support, see Add another.