Identicons are those icons based on a user IP or name or so which provide an automated avatar... just like the avatar icon on StackOverflow. Here are some available systems (hat tip to Roger Browne):
- http://haacked.com/archive/2007/01/22/Identicons_as_Visual_Fingerprints.aspx
- http://digitalconsumption.com/forum/Visiglyphs-for-IP-visualisation
- http://www.shamusyoung.com/twentysidedtale/?p=1462
- http://turnyournameintoaface.com/ [didn't provide an API for this, but considering generated pics are gender specific...]
- http://scott.sherrillmix.com/blog/blogger/wp_monsterid/
Are there more?
I believe SO uses Gravatars