Drupal is a free software package that allows an individual or a community of users to easily publish, manage and organize a wide variety of content on a website. Tens of thousands of people and organizations are using Drupal to power scores of different web sites.

• Community web portals
• Discussion sites
• Corporate web sites
• Intranet applications
• Personal web sites or blogs
• Aficionado sites
• E-commerce applications
• Resource directories
• Social Networking sites

As for me - it's main CMS platform that I'm using for creating sites. About a year ago I was close to hating this CMS because of it's complexity for developers but now, after a year of studying it I think that Drupal is "Most likely change the world" CMS potential winner of SourceForge contest.