Techniques are presented for automatically selecting information sources that are most relevant to user queries. Results of searches returned by information sources for queries are analyzed and the information sources are ranked based on this analysis. The information sources that have high rankings for a query are subsequently used to search for relevant results. This process can be adaptive, as the returned results of old queries can be analyzed at a later date to update the ranking of the information sources, automatic searches can be performed to update the ranking of the information sources, new queries can be used for analysis and stored, new information sources added, and old information sources deleted. A linguistic library is used to store personal categories for one or more users and general categories. Each category is associated with keywords and ranked lists of information sources. The library also contains general categories, taxonomies, and dictionaries.