http://www.technorati.comTechnorati is an Internet search engine dedicated to the world of weblogs (or blogs). As of December 2005, Technorati indexes over 23 million weblogs. Technorati was founded by Dave Sifry and is headquartered in San Francisco, California, USA. Tantek Çelik is Chief Technologist.
Open Source
Technorati uses and contributes to open source software. Technorati has an active developer community, many of them from open source culture. Sifry himself is a major open source advocate. Technorati includes a public developer's wiki, where developers and contributors collaborate, as well as various open APIs.