Trello is the most-well known project management tool due to its simplicity and extended free plan. The main idea behind the program that you can move your task cards in different columns that can simply represent To-do, In progress and Done statuses, or a more complex set up, like members of an outsourced team.
However there are plenty of other tools out there, some with really hot features and also with available free plan. I truly recommend you to check out these Trello alternatives and find your favourite that works best for you and for your team.
Here is a full overview of your project management tool options besides Trello.