1. A method comprising: by one or more computing devices, accessing a contacts list comprising one or more contacts in an address book of a first user; by one or more computing devices, accessing a data store for existing social-graph information between each contact in the contacts list and the first user; by one or more computing devices, accessing communication-history information for each contact in the contacts list, the communication-history information for a contact indicating a frequency of communication between the first user and the contact; by one or more computing devices, determining a usage frequency for each of one or more communication channels for each contact in the contacts list based on the communication-history information; by one or more computing devices, determining a social-proximity score for each contact in the contacts list based at least in part on the social-graph information, weighted average of the usage frequency of each of the communication channels, and one or more user-declared relationship types between the first user and other contacts of the contacts list; by one or more computing devices, ranking the contacts in the contacts list based at least in part on the social-proximity scores; and by one or more computing devices, providing the contacts list for display with the contacts as ranked based at least in part on the social proximity scores.