The drupal galaxy of sites

http://www.drupal.org : main site

http://api.drupal.org/ : reference manual

http://groups.drupal.org/ : community groups (SIGs, LUGs)

http://themes.drupal.org/ : theme demonstration site, à la CSS Zen Garden

http://www.drupaltutorials.com/ : wiki for the development of the Drupal curriculum

irc://irc.freenode.net/#drupal : IRC chat about Drupal development

irc://irc.freenode.net/#drupal-support : IRC chat about Drupal support for site builders

irc://irc.freenode.net/#drupal-themes : IRC chat about Drupal theme creation

irc://irc.freenode.net/#drupal-courseware : IRC chat about the Drupal curriculum (by appointment only)

irc://irc.freenode.net/#drupal-ecommerce : IRC chat about Drupal e-commerce (usually empty, use #drupal instead)

http://www.drupaled.org/ DrupalED for Education

http://drupalart.org/ DrupalART for Artists and Musicians

http://civicspacelabs.org/home/developers/download CivicSpace: Drupal with CiviCRM

http://www.drupalecommerce.com/ Demo / advocacy site

http://www.drupalancers.com/ Marketplace for professional Drupal consulting (but see also http://drupal.org/forum/51)

http://drupaltopsites.com/

http://top.drupalsites.net/

http://www.drupalsites.net/

http://wiki.audean.com/ this wiki

http://blog.riff.org/drupal FGM's blog section about Drupal

To be listed: too many !