Todoist is an easy-to-use task management service that I first tried on the web a couple of years ago. When I tried it then I was impressed by its clean design and intuitive user interface. Todoist is also available to use as an iPad app (Android and Windows apps are available too). The free iPad app seamlessly syncs with your Todoist online account.
When you create projects and assignments in Todoist by default they are arranged chronologically. You can reordering them by simply selecting an moving them up or down. The free version of Todoist provides twelve color coded labels that you can apply to tasks and projects.