ToDo List Widget is a Widgets software developed by Yahoo! Inc.. After our trial and test, the software is proved to be official, secure and free. Here is the official description for ToDo List Widget:

A Simple To-Do List that lets you dynamically add and remove items. Drag items up or down to organize your list and the Widget remembers the order. Choose from preset colours (or pick a custom colour) to tag your items your own way. You might choose pink for Things To Do for work and yellow for home - it's up to you!
Features:
Drag-and-drop reordering of Items
Colourize each to-do item
Adjustable Font Size
Custom size
Widget comes with 5 skins for any taste
No need for external calendar apps, this Widget just works!