Drupal

Drupal

Drupal Gardens

http://www.drupalgardens.com/

Drupal allows an individual or a community of users to easily build websites to manage users, site structure and content. Hundreds of thousands of people are using Drupal to power over 1% of the world's web sites— and now you can too using these features and a little imagination. Check out What's new for the latest enhancements. With Drupal Gardens, there's nothing to install and no servers to manage. We take care of everything on the backend so you can focus on building great sites.

Official Drupal Website

http://www.drupal.org

Here you can access an in-depth documentation, download Drupal and its elements (modules, themes, etc.) and interact with the Drupal community (Q&A, troubleshooting, etc.): "The passionate volunteer Drupal community is on hand to give support via various vibrant IRC channels, in the forums, and face to face at Drupal events. The community has also created Documentation for Drupal, which covers major topics related to working with Drupal. The worldwide community drives the innovation that makes Drupal the preferred choice for web developers and site owners. Everybody can get involved and make a difference to Drupal."