The Webometrics Ranking of World Universities is a ranking system for the world's universities based on both the volume of Web contents and the visibility and impact of these web publications according to the number of external inlinks (site citations) they received. The ranking is published by the Cybermetrics Lab, a research group of the Spanish National Research Council (CSIC) located in Madrid. The aim of the Ranking is to improve the presence of the academic and research institutions on the Web and to promote the open access publication of scientific results. The ranking started in 2004 and is updated every January and July and provides Web indicators for more than 12,000 universities worldwide (Wikipedia).
In addition to universities, repositories, hospitals, business schools and researchers centers are also ranked.