1. A method comprising: receiving a search request from a first user; performing a search based on the search request; providing a set of search results; providing a set of categories for organizing the set of search results, wherein each category is identified based, at least in part, on one or more search results; organizing the set of search results into a hierarchy of categories, the hierarchy including at least one category from the set of categories; displaying at least a portion of the hierarchy of categories to the first user; receiving a request from the first user to modify the hierarchy of categories; modifying the hierarchy of categories in accordance with the request from the first user; associating the modified hierarchy of categories with a user profile for the first user; storing the modified hierarchy of categories associated with the first user to provide a customized hierarchy of categories to the first user for use in response to subsequent search requests from the first user; and providing a customized category hierarchy for the first user based on the user profile for the first user in response to a subsequent search request from the first user.