1. A method of providing a graphical display of a user's computing activity, comprising: at a search engine having one or more processors and memory storing programs executed by the one or more processors: receiving from a client system, distinct from the search engine, a request for displaying the user's computing activity over a unit of time for one or more activity types in accordance with one or more user-specified criteria, the unit of time having a plurality of sub-units of time; identifying computing activity within the user's computing history of the one or more activity types which satisfies the one or more criteria; identifying, for each respective sub-unit of time of the plurality of sub-units of time, a respective first activity number corresponding to the volume of identified computing activity which satisfies the one or more criteria in a subset of the user's computing history corresponding to the respective sub-unit of time; associating one of a plurality of visually distinctive indicators to each of the plurality of sub-units of time in accordance with the respective first activity number for each respective sub-unit of time, wherein each of the plurality of visually distinctive indicators corresponds to a distinct range of values of the respective first activity number; and providing to the client system, in response to the request, information for graphically displaying at the client system the unit of time and the plurality of sub-units of time, wherein displaying each respective sub-unit of time includes displaying the associated one of the plurality of visually distinctive indicators to graphically represent the volume of the user's computing activity which satisfies the one or more criteria for the respective sub-unit of time.