Drupal is one of the world's most popular Content Management Systems available on the market. A lot like Wordpress, Drupal allows clients to edit their own site with no prior technical knowledge.
Drupal is an open source platform meaning there is no set up fees and users from all over the world are constantly working on it to improve and update it. Drupal works by way of adding open-source modules. The main benefit of this is that if you have an idea of the functionality that you wish to see on your own site, there is a good chance that functionality has already been created and documented by the community, so all it takes is some light customisation.
Drupal is perfect for a community based project (such as a small social network) or even an e-commerce type project. It can help your small organisation get online or improve your multi-nationals user experience. If it's good enough for President Obama it's certainly good enough for us.
Here are some well known sites built with Drupal: