A friend of mine works in a small team (5 people) and they don't have any application to keep track of who is working on what.
There are a lot of questions asked here about application for project management applications, and it's hard to tell if there is one that satisfies those requirements:
- open-source
- web-based
hierarchical to-do's (ie. sub-tasks)

- each user is allowed to create their own project
The goal is simply for everyone on the team (managers and employees) to have a rough idea about employees' workload. Nothing fancier.