One of my favorite project management tools has to be Asana. It has a super easy user interface and gives you the opportunity to assign owners to tasks and subtasks and sub-subtasks.
One great advantage that I find over other tools, like Trello, is that you can add due dates to subtasks. Additionally, you can set tasks up either in lists or boards depending on your needs. Lastly, the Asana app is easy to use and helps you stay abreast of your tasks on the go.