A navigation bar is provided for switching between modules within an expanded communication service such as email, calendar, contacts, tasks, etc. and for presenting preview peeks associated with each module to a user. A temporary preview of a module may be provided upon a hover action over predefined navigation bar locations such as icons and/or textual identifiers without actually needing to switch to a module. The preview may also be docked or pinned to a location on the main user interface so that it is displayed within the main user interface. New or interesting activity within each module may be highlighted by displaying an information badge next to a module name, for example.