DBpedia

DBpedia allows you to ask sophisticated queries against Wikipedia and link other datasets on the web to Wikipedia data. It provides a number of services around the extracted data, like DBpedia mobile, a SPARQL endpoint, a faceted browser, a number of mappings to external ontologies, an ontology itself, etc. The project was started at the Free University of Berlin and Leipzig University, in collaboration with OpenLink Software. It is made available under free licences (CC-BY-SA), allowing others to reuse the dataset; it doesn't however use an open data license to waive the sui generis database rights. Wikipedia articles consist mostly of free text, but also include structured information embedded in the articles. This structured information is extracted and put in a uniform dataset that can be queried.