1. One or more computer-storage devices accessible by a computing device having computer-executable instructions embodied thereon that, when executed by a computing device, cause the computing device to perform a method of augmenting Web-based search results with relevant content received from third-party applications, the method comprising: registering each of a plurality of third-party applications to obtain an indication of one or more entity types associated with the each registered third-party application of the plurality of third-party applications; receiving an annotated search query, the annotated search query comprising at least an inputted search query and at least one entity type determined to be associated with the inputted search query; in response to receiving the annotated search query, receiving at least one search result from at least a first third-party application of the plurality of third-party applications, wherein the at least one search result from the at least first third-party application is relevant to the at least one entity type associated with the inputted search query; and presenting the at least one search result from the at least first third-party application on a results page.