GD Star Rating is a WordPress plugin that allows you to set up rating and review system for posts, pages, and comments in your blog. You can set many options for displaying the rating stars, and also add widgets into the sidebars for displaying top ratings and other statistics generated by the plugin. The plugin includes advanced settings panels that will allow you to control many aspects of rating. The plugin also supports multiple ratings.
Slidematch is a media rating, contextual retrieval, peer recommendation, and library management system for music, video, movie, and book impressions. It adds value to your existing media player by enabling you to easily record detailed impressions, retrieve content appropriate to what you are currently doing, and interact with friends.