There are a lot of tasks management software available. I suggest Team Task Manager, very useful in effectively organizing and planning so improved productivity can be achieved. Using this tool, you can create projects, hierarchical task groups and tasks and assign individual access rights for each project. It also enables you to share and edit documents securely.
[edited by: LifeinAsia at 4:20 pm (utc) on Aug 7, 2013] [edit reason] no URLs please [/edit]
If you recommend some software, please describe how the software has benefited you or why you are recommending it. Often, without trying out software, it is very difficult to know how easy it is to use (or even install), and experiences from other users helps narrow down the short list.
I'm using two excellent apps at the moment. KanbanFlow helps me keep track of tasks and I can share what I need with my team. It has a great interface and we now tend to think of our whole lives as a series of Kanban projects! Newly discovered and quite awesome is Workflowy. It has taken me a few weeks to really understand the power of it but I love it and use it to keep all my "to do" lists organised. You can share but at the moment I keep this to myself and use it for brain-dumping, brain-storming, planning etc.