Rate

Most ratings plugins contain too much code: inline JavaScript, messy markup, weird CSS. Rate is simple, hardly intrusive, and completely overridable.

A Post/Page/Custom Post Type’s rating is the average of all comment ratings. A user can leave a rating when commenting, and change that rating inline after leaving a comment (if logged-in or Cookie’d).

Don’t be afraid to play around and extend the code: drop a rate.css file in your theme directory and mine won’t even load (by default, Rate stars are transparent with a white border, so you can use background-color to set your stars’ colors)!

Read More: http://scottctaylor.wordpress.com/2010/11/30/new-plugin-rate/