Flag is a flexible flagging system that is completely customizable by the administrator. Using this module, the site administrator can provide any number of flags for nodes, comments, or users. Some possibilities include bookmarks, marking important, friends, or flag as offensive. With extensive views integration, you can create custom lists of popular content or keep tabs on important content.

The Fivestar voting module adds a clean, attractive voting widget to nodes in Drupal 5 and 6. Developed by Lullabot and an officially supported module in Acquia Drupal.
It features:

#D7CX: I pledge that VotingAPI will have a full Drupal 7 release on the day that Drupal 7 is released.

VotingAPI helps developers who want to use a standardized API and schema for storing, retrieving, and tabulating votes for Drupal content.

Among other things, it supports: