I've installed a couple of Drupal modules on the site including Feedback, users guestbooks, invite and my buddylist. It seems with the modules help, Drupal based site has all functionality one could think of. However I could not find a good voting solution (a la digg.com) for Drupal. In fact in version 4.6 it had comments voting already built-in, but later it was removed from the core.
