Rich Snippets must be working out for Google, they continue to expand the use of the feature. In short, rich snippets let webmasters markup their HTML and content to give Google a bit more meta data so Google can enhance the snippets to displayed in the Google search results.
Google has now enabled rich snippets for shopping sites. Google said:
In time for the holiday season, we now support rich snippets for shopping (e-commerce) sites! As many of you know, rich snippets are search results that have been enhanced using structured data from your web pages. Our new format shows price, availability, and product reviews on pages offering a product for sale.
Here is an example of a rich snippet used for a shopping site in the Google search results:
How does it work? Well, you can read the help document on this which explains you have two options.
Option 1: Provide a Merchant Center feed.
Option 2: Add markup to your site.
Forum discussion at WebmasterWorld.