Rating-Widget adds ratings to your posts, pages, and comments. It is CSS3 complaint and lets you create unlimited thumb and star items. There is no limit on how many votes you can gather. You can customize your ratings and its placement. The plugin also has a “top rated” widget that you can add to your sidebar easily. The pro version offers even more features, including support for Rich Snippets, SSL support, and analytics.
Rating-Widget is simple looking and easy to implement. Not all sites might need ratings but if you do, this plugin has you covered.