Get started by downloading the official Drupal core files. These official releases come bundled with a variety of modules and themes to give you a good starting point to help build your site. Drupal core includes basic community features like blogging, forums, and contact forms, and can be easily extended by downloading other contributed modules and themes.
Following Drupal core development
For announcements specifically around Drupal 8 (the unreleased version that is currently in development), please see http://drupal.org/community-initiatives/drupal-core and the Drupal 8 Initiatives group (RSS feed).
You can give back to the project by making a donation to help fund the Drupal.org website.