1. In a computer system including an address book application and a plurality of computer applications that are independent from the address book application, a computer-implemented method for dynamically autocompleting a data entry field for a user into any of the plurality of independent computer applications, the method comprising: monitoring usage data of the user as the usage data is directed to any of the plurality of independent computer applications; extracting contact information from the usage data; storing the contact information as contact entries to create an address book for the user, wherein the address book is configured to allow the user to access and edit the contact entries in the address book; determining that an input of data is required in the data entry field of one of the plurality of independent computer applications; determining a valid type of contact entry that is acceptable by the independent computer application requiring the input of data; ranking the contact entries in the address book based at least on current locality information of the user and the valid type of contact entry to determine one or more data candidates from the address book for the input of data in the data entry field; and autocompleting the input of data into the data entry field of the independent computer application with at least one of the data candidates from the address book.