I’d recommend you to try Wrike! (http://www.wrike.com) It’s really powerful project management software with real-time newsfeed, Gantt chart, Workload view, email integration and many other great features – actually all you need for efficient project management. The app is online, so all team members get notified about all task updates in real time both in Wrike’s Activity Stream and via email. As for the sub-projects, in Wrike all tasks are organized into folders (it can be projects, departments, clients etc), so subfolders may be used as subprojects.