social networking drupal

http://drupal.org/node/206724

file sharing on drupal

http://drupal.org/project/cck
http://drupal.org/project/views
http://drupal.org/project/media_mover
http://drupal.org/project/filebrowser
http://drupal.org/project/webfm

Uploading images Drupal

http://drupal.org/project/image

Digg clone with Drupal!

The next evolution.
http://drupal.org/project/drigg