18. A non-transitory computer storage medium encoded with a computer program, the program comprising instructions that when executed by data processing apparatus cause the data processing apparatus to perform operations comprising: identifying structured document data in a document, the structured document data including information identifying one or more entities and, for each entity, a resource locator specifying a resource location of a resource for the entity; determining one or more terms associated with a particular entity of the one or more entities, the determining the one or more terms comprising: identifying anchor text in the structured document data, the anchor text including the one or more terms; determining a number of documents in a set of documents that include the identified anchor text; and determining that the number of documents exceed a threshold number of documents; generating one or more synthetic queries from the structured document data, the generating comprising generating a synthetic query that includes the anchor text; storing the synthetic query in an augmentation query data store; identifying search results that are relevant to the synthetic query; associating, in the augmentation query data store, the identified search results and the resource for the particular entity with the synthetic query; and storing at least a portion of the identified search results and a search result for the resource for the particular entity in a cached search results store for use in an augmented search operation, wherein the stored search results are provided with other search results in response to the augmented search operation, the other search results being responsive to a received query for which the augmented search operation is performed.
18. A non-transitory computer storage medium encoded with a computer program, the program comprising instructions that when executed by data processing apparatus cause the data processing apparatus to perform operations comprising: identifying structured document data in a document, the structured document data including information identifying one or more entities and, for each entity, a resource locator specifying a resource location of a resource for the entity; determining one or more terms associated with a particular entity of the one or more entities, the determining the one or more terms comprising: identifying anchor text in the structured document data, the anchor text including the one or more terms; determining a number of documents in a set of documents that include the identified anchor text; and determining that the number of documents exceed a threshold number of documents; generating one or more synthetic queries from the structured document data, the generating comprising generating a synthetic query that includes the anchor text; storing the synthetic query in an augmentation query data store; identifying search results that are relevant to the synthetic query; associating, in the augmentation query data store, the identified search results and the resource for the particular entity with the synthetic query; and storing at least a portion of the identified search results and a search result for the resource for the particular entity in a cached search results store for use in an augmented search operation, wherein the stored search results are provided with other search results in response to the augmented search operation, the other search results being responsive to a received query for which the augmented search operation is performed. 24. The non-transitory computer readable storage medium of claim 18 , wherein associating, in the augmentation query data store, the identified search results and the resource for the particular entity with the synthetic query comprises associating the resource for the particular entity with the synthetic query independent of a relevance measure of the resource to the synthetic query.