1. In a computer network that includes at least two computers communicatively coupled to each other, a system for sharing knowledge objects among the registered users of the computer network comprising: a means for maintaining and updating a collection of local or private knowledge objects managed by users, wherein each individual user can access any of the private knowledge objects directly; and a means for maintaining and updating a collection of published knowledge objects contributed by the users, wherein any of the users can access any of the published knowledge objects by entering a unique user identification; and a means for maintaining and updating a collection of listed knowledge objects contributed by the users, wherein any of the listed knowledge objects can be identified but cannot be accessed by any of the users other than the user who contributed the listed knowledge object unless the user who contributed the listed knowledge object authorizes the proposed access.