A social search engine is very much like a ‘traditional’ search engine in that well written, SEO friendly content is indexed in traditional ways in Google, Yahoo and Bing.

Unlike traditional search engines, social search engines can take a number of other factors into play other than SEO content, for example:

• How many times people share the link of an article for example, via social networks such as Twitter and Facebook
• How many people use social bookmarks to re-publish the link
• Tagging and connecting articles and posts through blogs/social networks
• Voting on articles posted to certain news wires (like Go Articles, Wikio)

Here is a selection of social search engines:
http://topsy.com/
http://www.icerocket.com/
http://www.whostalkin.com/
http://www.samepoint.com/
http://www.scoopler.com/
http://www.mamma.com/
http://www.gravee.com/