There are many free web based task managers and online todo lists. These online task tools are great because they provide portability and ease of using anywhere. Which one to use? If you are looking for simplicity and ease of use, then best task tools are Remember the Milk (RTM) and Todoist.
Both web tools are great. Advantage of Remember the Milk is that it is slightly easier to use and more intuitive than todoist. Also, RTM has great fan following so you can get some good tips in forum. But RTM does not support projects and subtasks. Todoist support projects, subprojects, tasks, and subtasks. So Todoist can be used as an efficient project management tool also.
Biggest disadvantage of these task managers is lack of support for dependent tasks.
Here are few more task managers worth looking, if any of the above two do not support features you are looking for.
