Tags are playing a major role on most of the Web 2.0 websites. Every Blog, bookmark or Photo has to have different tags associated with it. There are several tag search engines.
These search engines use different sources to fetch tags; some of them are listed below:
Google news, Flicker, IceRocket, Wikipedia, 43things, Youtube. de.licio.us, Technorati, Feedster, Furl and so on.