Asana is a web and mobile application designed to enable teamwork without email. It was founded by Facebook co-founder Dustin Moskovitz and ex-engineer Justin Rosenstein, who both worked on improving the productivity of employees at Facebook. Asana is a teamwork communication manager. The product supports many features, including workspaces, projects, tasks, tags, notes, comments, and an inbox that organizes and updates information in real-time.

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.

http://www.asana.com