The product is designed to enable individuals and teams to plan and manage their projects and tasks without email. Each team gets a workspace. Workspaces contain projects, and projects contain tasks.
In each task, users can add notes, comments, attachments, and tags. Users can follow projects and tasks, and, when the state of a project or task changes, followers get updates about the changes in their inboxes. (Source: http://en.wikipedia.org/wiki/Asana_software)
Give it a try. Free for teams of up to 15 members with unlimited project.