DoIt!

Do It is a very simple application that can help you manage your to-do lists. The application allows you to organize pending tasks by category, so you can easily find them.

For every task, you can add brief notes, drag a file or URL to link the note to, select a priority (low, medium, high), and establish a deadline to complete it. Every task has an empty box next to it, which you can check once you complete the task. Sadly, the application doesn't include reminders.

You can create as many categories as you want, and you can easily switch between them by clicking the arrow at the top of the application. When a task is marked as completed, you can set the program to change its priority to low, delete it after a certain number of days, and move it to a certain category. The notes can be saved in multiple formats, backed up, exported and printed. The program is very easy to use, also it has a clean and simple user interface, so it won't give you any trouble.

In short, if you are looking for a simple application to organize to-do lists in one place, Do It may be a good choice.