1. A method comprising: storing user interaction information describing user interactions between a viewing user of a social networking system and additional users of the social networking system through a messaging application associated with the social networking system; storing group interaction information describing group interactions between the viewing user of the social networking system and one or more groups of users of the social networking system, each group including a plurality of users through the messaging application associated with the social networking system; determining user interaction scores for each of the additional users, each individual user interaction score indicating a likelihood of the viewing user interacting with an additional user based at least in part on the individual user interactions between the viewing user of the social networking system and the additional user; determining group interaction scores for each of the one or more groups of users, each group interaction score indicating a likelihood of the viewing user interacting with a group based at least in part on group interactions between the viewing user of the social networking system and the group; ranking the additional users and the one or more groups in a single ranking based at least in part on the user interaction scores and the group interaction scores, the single ranking including at least one of the additional users and at least one of the one or more groups ranked relative to each other based on the user interaction information and the group interaction information; selecting one or more of the additional users and at least one of the one or more groups as suggested contacts for the messaging application, wherein the selecting comprises: selecting a contact as an additional user or a group of users having at least a threshold position in a ranking; and determining an order of the additional users and at least one of the one or more groups included in a set of contacts based on the user interaction scores associated with each of the additional users and the group interaction scores associated with at least one of the one or more groups included in the set; and communicating information identifying the suggested contacts to a client device of the viewing user, the client device presenting the suggested contacts to the viewing user in an interface of the messaging application that presents information associated with contacts of the viewing user.
5. The method of claim 1 , wherein communicating information identifying the suggested contacts to the client device of the viewing user comprises: communicating information describing the order of the one or more of the additional users and at least one of the one or more groups included in the set of one or more of the additional users and at least one of the one or more groups to present the set of one or more of the additional users and at least one of the one or more groups in the interface of the messaging application based on the order.