drush_multi is an extension to the Drupal Shell aka drush.

How to effectively build websites with Drupal. This session is showing some useful tools and good methods on how to manage site building more productively. How does a complete workflow for professional (team) site builders could look like. Beginning from local development over testing and staging sites to late changes on online live sites.
Learn about basic concepts of Drush (Drupal Shell), Features and using version control for your Drupal codebases.

Where do you start when upgrading a website with an active community around it? How do you preserve the data for thousands of users and nodes? How do you move away from obsolete modules? How do you limit downtime to a few hours? These are common questions we have to answer when upgrading websites from Drupal 5 to Drupal 6 and adding new functionality on top of it!