1. A method comprising: maintaining, in a storage device and on behalf of a first user, a list of identifiers representing one or more other users of the communication system and for which online presence information is made perceivable through the list, the list including one or more categories into which listed identifiers are categorized based on attributes associated with the listed identifiers, each of the one or more categories reflecting attributes other than online presence; accessing, from the storage device, at least one attribute associated with an identifier; accessing at least one attribute stored relative to at least one of the one or more categories included within the list; comparing the at least one attribute associated with the identifier to the at least one stored attribute; automatically adding, using at least one processor, a new category in the list based on a result of the comparison; and categorizing the identifier into the new category, wherein adding the new category includes making perceivable a pre-existing category that was previously hidden.