If you are running more than one Drupal site, you can simplify management and upgrading of your sites by using the multi-site feature. Multi-site allows you to share a single Drupal installation (including core code, contributed modules, and themes) among several sites.
What is CiviCRM ?
CiviCRM is a web-based, open source CRM system, designed specifically to meet the needs of advocacy, non-profit and non-governmental organizations. Elected officials, professional/trade associations, political campaigns and parties, government agencies, and other similar organizations are among its growing number of enthusiastic users.
All you need to know is "If X then Y" and Rules. Code less do more. Easy interface, more control for admin, integration with workflows and mails. What more can you ask for ?
CCK, Views and Panels have been rightly called as the trilogy of Drupal. But there is more to it. It's actually the Quartet. And Rules is the lesser known module among the quartet. But for those who know Rules, Rules Rock I mean Rules Rule ;) So first lets learn Rules and then break them.