The “stars” and other bits of data that make their way into Google’s search results come under their umbrella term, “Rich Snippets”. You can specify them as Microformats or RDFa and they currently look at information about reviews, people, products, and organisations.

http://www.google.com/support/webmasters/bin/answer.py?answe...

http://knol.google.com/k/google-rich-snippets/google-rich-sn...