For web developer

Starbox is a star rating library built on Prototype Javascript framework which you can use to create most types of star rating systems with 1 png image.

In order to add some extra effects to the star rating code, you can add script.aculo.us as well (sample codes can be found in the Starbox website).

Some features of Starbox:

Re-rating allows you to adjust your previous rating.
Easily saving your rating with Ajax using the build in callback.
Styling the Starbox based on status (hover, rated and locked).
Good seperation of Javascript, CSS and images.
A ghosting bar that tracks your average.
Batched building of Starboxes based on cached overlay images.

Requirements: Prototype 1.6+, script.aculo.us for effects.
Compatibility: All Major Browsers

PHP / MySQL Ajax Star Rating Script is an unobtrusive script (which will work if the JavaScript is turned off) which you can easily integrate it with your current content.

This star rating script is not tied to any CMS so you will need some coding skills to integrate it.

It supports configuration of howmany stars will be shown in the front-end.

Requirements: No Requirements

Rabid Ratings is an excellent Mootools based star rating solution which comes with hearts instead of stars by default.

Installing Rabid Ratings is very easy by simply telling the code the database username, password, host address and including a php tag in where we want the ratable item. Rating data is shown in decimals & in heart images Also, the number of votes are displayed too.

Most AJAX ratings widgets use star and half-star images with mouse over events on each star. Rabid Ratings uses a reverse alpha-transparent PNG as a background image to achieve infinitely complex precision (ie, 1.23 stars) and robust visual effects with a very low overhead.

Requirements: PHP 4+, Mootools 1.2

Control Suite is a set of 6 high quality widgets and controls built with the Prototype JavaScript framework.

Each script is well tested, highly extensible and unobstrusive.

Suite has these widgets and controls:

Tab
Modal
TextArea
Select Multiple
Rating
Progress Bar

Different approach to star rating:

Suite is very well documented. You can easily reach the details of the APIs and this makes the product much more usable.

Requirements: Prototype JavaScript Library
Compatibility: All Major Browsers

This is an Ajax star rating script that uses cookies, SQL & PHP.

In general star rating scripts have 5 stars & users need to choose one of them. This one has again 5 stars but the selection is percentage based which enables users to select from 1% to 100%.

The website presenting the script, Nomadic Functions, has also some other free scipts that you may want to check, like:

Color conversion library
DHTML color picker
Drag & drop & more..

Requirements: No Requirements
Compatibility: All Major Browsers

SharpPieces is a set of open source & free ASP.NET controls for improving the usability of the applications easily.

Currently there are 8 components:

ExtendedDropDownList
LiveGrid
FancyUpload
ImageCheckBox
Rating
DynamicImage
CaptchaImage
GradientButton

They are all are ready with native support for the latest framework (ASP.NET 3.5) and IDE (Visual Studio 2008).

Requirements: No Requirements

Star Rating System is a free PHP script for adding an Ajax star rating feature to a website.

It uses MySQL as the database & the interface can be styled via CSS.

It has various templates which enables you to create an Ajax or non-Ajax version (that rating can be completed via radio buttons but results are shown in stars).

Several demos for the script can be found here.

Requirements: PHP & MySQL
Compatibility: All Major Browsers

jRating is a very flexible jQuery plugin for quickly creating an Ajaxed star rating system.

It is possible to configure every detail from" the number of the stars" to "if the stars can represent decimals or not".

There is also an option to display small or big stars and images can be changed with any other file easily.

Although the plugin can be used with any scripting language, a PHP file that handles the requests is already included in the download package.

Requirements: jQuery
Compatibility: All Major Browsers