9. A computer system comprising: one or more computing devices; an interface of the one or more computing devices that is programmed to access a search history that identifies one or more search queries that were previously submitted to one or more search services by one or more client computing devices that are associated with a user; a reverse geocoder that is installed on the one or more computing devices and that is programmed to identify a geographic location to which future voice input from the user is likely to relate based at least in part on the search queries included in the search history, wherein the geographic location is identified independent of a current geographic location of the one or more client computing devices; and a grammar index that is accessible by the one or more computing devices and that includes an index that correlates geographic locations to a plurality of grammars; a grammar selector that is installed on the one or more computing devices and that is programmed to select a first grammar from among the plurality of grammars, before performing automated speech recognition on voice input from the one or more client computing devices, based at least in part on the geographic location identified by the reverse geocoder based at least in part on the search queries included in the search history, wherein the first grammar includes a vocabulary that is relevant to the geographic location that is identified based at least in part on the search queries included in the search history; wherein the interface is further programmed to output information that identifies the first grammar, wherein the outputted information causes a grammar used to analyze subsequently-received voice input from the one or more client computing devices to be changed to the first grammar.
9. A computer system comprising: one or more computing devices; an interface of the one or more computing devices that is programmed to access a search history that identifies one or more search queries that were previously submitted to one or more search services by one or more client computing devices that are associated with a user; a reverse geocoder that is installed on the one or more computing devices and that is programmed to identify a geographic location to which future voice input from the user is likely to relate based at least in part on the search queries included in the search history, wherein the geographic location is identified independent of a current geographic location of the one or more client computing devices; and a grammar index that is accessible by the one or more computing devices and that includes an index that correlates geographic locations to a plurality of grammars; a grammar selector that is installed on the one or more computing devices and that is programmed to select a first grammar from among the plurality of grammars, before performing automated speech recognition on voice input from the one or more client computing devices, based at least in part on the geographic location identified by the reverse geocoder based at least in part on the search queries included in the search history, wherein the first grammar includes a vocabulary that is relevant to the geographic location that is identified based at least in part on the search queries included in the search history; wherein the interface is further programmed to output information that identifies the first grammar, wherein the outputted information causes a grammar used to analyze subsequently-received voice input from the one or more client computing devices to be changed to the first grammar. 13. The computer system of claim 9 , wherein the one or more client computing devices include a smartphone.