http://technorati.com - a WeblogEcosystemService
Technorati tracks weblogs and keeps a database of the links between weblogs and from weblogs to other sites. Most notably, this enables it to provide InboundLink data for individual weblogs or webpages, which they call the "cosmos". This enables authors to find out who has linked to their writing.
The database also enables Technorati to list which links appear on the most weblogs. Weblogs that receive the most links appear in the Technorati Top 100 - http://technorati.com/live/top100.html. See LinkRank.
Technorati wants to provide Web services that other developers can build upon to provide services of their own, mainly through the Technorati API. The developers' playground is at http://developers.technorati.com/wiki/.
Technorati, inc. was founded by DavidSifry in 2003 (?).