Thanks to the support of Google Summer of Code'09, I was able to develop the Recommender Bundle for Drupal, which includes the following modules:
http://drupal.org/project/recommender
http://drupal.org/project/history_rec
http://drupal.org/project/fivestar_rec
http://drupal.org/project/voting_rec
http://drupal.org/project/uc_rec
http://drupal.org/project/similargroups
http://drupal.org/project/media_rec (not developed)
