Until
May 3, 2012 at 11:59pm PT O'Reilly are offering books on Drupal at 50% off at
http://shop.oreilly.com/category/deals/drupal.do
From Wikipedia at
http://en.wikipedia.org/wiki/Drupal "
Drupal (
/ˈdruːpəl/) is a
free and open-source content management system (CMS) and
content management framework (CMF) written in
PHP and distributed under the
GNU General Public License.
[2][3][4] It is used as a
back-end system for at least 1.5% of all
websites worldwide
[5][6] ranging from personal
blogs to corporate, political, and government sites including
whitehouse.gov and
data.gov.uk.
[7] It is also used for
knowledge management and business collaboration.
Drupal runs on any
computing platform that supports both a
web server capable of running PHP (including
Apache,
IIS,
Lighttpd,
Hiawatha,
Cherokee or
Nginx) and a
database (such as
MySQL,
MariaDB,
PostgreSQL,
SQLite,
MongoDB or
Microsoft SQL Server) to store content and settings. Drupal 6 requires PHP 4.4.0+ while Drupal 7 requires PHP 5.2 or higher.
[4]"