1. A method for tag management by a client-side agent on behalf of a user of a client-side portal application providing access to a set of services that includes provisions for collaborative tagging of content, the method comprising: accessing one or more data repositories configured to maintain one or more separate sets of tags for the user, the sets of tags including a set of tags corresponding to each service of the set of services in each role of one or more user roles and specifying available vocabulary which is to be used to tag content at a user specified service and a user specified role; displaying the vocabulary corresponding a user-specified service and a user-specified role to the user; converting message formats and transport protocols between the client-side agent and the one or more data repositories via a messaging intermediary in communication with the one or more data repositories and configured to provide access to the one or more data repositories and to provide for communication with the set of services; and communicating with the user-specified service to post tags selected by the user from the vocabulary to content at the user-specified service, wherein the user can only post tags selected from the vocabulary for the user specified services and the user specified roles.