MiniTask is a simple application that allows you to create to-do lists in a snap. You just need to type a new task in the dialogue and then you can add more tasks before or after that task. When you complete any task, you can simply mark it as done by checking the box. You can also separate tasks by categories by adding what it's called a "separator" in which you can type any name for the category. "Separators" can be edited, removed or collapsed whenever you want. If you collapse a separator, the tasks included under it will be hidden.
A good thing about this program is that you can add alarms for specific tasks, so you won't forget to carry them out. The tasks can also be copied to the clipboard as HTML or TXT, and you can print them, if you want. Unfortunately, you won't be able to customize the font size, type or color from the program, but you can do it from the user directory, which is not very easy. The user interface is very simple and minimalist, and very easy to use.
In short, if you are looking for a simple application to create and manage to-do lists very easily, MiniTask may work for you.