Gestion de Projet will assist you in creating Gantt graphs easy and fast. Gestion de Projet is also ment to simulate projects' workload according to hypothesis of tasks to do, to their respective length and their succession in time.

If you do not know Gantt graph, let me just tell you that it is a graphical way of showing projects that has no real competitor to get a clear appearance of the ongoing of a project. This organisation tool helps in knowing the state of the different tasks of the project, and more precisely to put to evidence, for each task, the worked time, the still to work time.
Don't forget that a good project starts with a good plannification of it!