Here are some tutorials that should help you get started with the Rules module. Feel free to add further tutorials.

You can also have a look at the workflow-ng tutorials (for drupal 5), but note that some things might have changed since then.

Also the presentations 09-2009 at the Drupalcon Paris 2009 - Video and 11-2009 at the Drupalcamp Vienna 2009 showed how to implement two use cases and provide ready to use feature modules:

• React on user inactivity
• A basic publishing workflow