You can run multiple Drupal sites off one installation of Drupal. By doing so, you can use the same modules you used on other sites eliminating the need to install modules over and over as you build different Drupal sites. When one site is updated, all sites are updated.
Thank you for your interest. I apologize for any inconvenience this limited access causes. This online guide is now a book called Drupal: The Guide to Planning and Building Websites. The content of the guide is being updated, expanded, and edited. It will include tips for D6 and D7. I hope you will find it useful.
