Drupal is a content management system for building dynamic web sites offering a broad range of features and services.  Drupal facilitates user administration, publishing workflow based on user roles, discussion capabilities, news aggregation of content from external sources and publishing functionalities for content sharing purposes. Drupal is powerful, rich in features and configurability, it can support a diverse range of web projects from personal weblogs to large community-driven sites.

You can read more on the About Drupal page on the Drupal site. http://drupal.org/about

Drupal is open-source distributed under General Public License (i.e. free!) Supported by the Drupal community, you can make a contribution by something as simple as submitting bug reports.

Drupal is a well constructed platform due to the dedication of a large number of talented contributors and creator Dries Buytaert.  http://buytaert.net/

Is Drupal the right tool for the job?

Drupal is a powerful and flexible framework for building virtually any kind of website and  is a good candidate for:

• Flexibility - for example, you might start with a blog but want the option of adding other features like a wiki, electronic commerce, forums etc.
• Easily configured to interact with other sites or with other technologies
• It can easily handle complex forms and workflows
• Create your own content types
• Ability to quickly organize and display lists of information
•  Contributed modules available to address your requirements
• Quickly develop custom functionality
• Create web applications and mashups using third party API's

Drupal may not be the best choice:

If your sole requirement is to write a personal blog, wiki or host a discussion forum, you may also want to evaluate one of the more specialised platforms. A list of suggested list of platforms can be found on the Drupal page http://drupal.org/node/346217

How does Drupal compare to other content management systems?

Comparison sites offer a range of information. One such site is the CMS matrix which allows side by side comparisons of features - http://www.cmsmatrix.org/matrix/cms-matrix/drupal

Who’s using Drupal?

Just a few website shown on Dries Buyaert's site:

• Twitter
• Many government agencies and world leaders
• IKEA
• Telnet knowledgebase
• eBay
• Tate
• Yahoo style guide
• Digg
• Mensa
• NASA

For the full list go to  Dries site: http://buytaert.net/tag/drupal-sites

User guides and support

While Drupal is easy to install, configuration may take a bit more time. Drupal documentation is good and a strong community is available for question and answer via Drupal user forums.

http://drupal.org/documentation