Get it: ToDo Widget
If you're of the GTD mindset (that's get-things-done, for the uninitiated) you pretty much need ToDo. This widget lets you track everything on your to do list. You can create multiple lists for different purposes, and even share the lists with your friends. I think this one really speaks for itself, so I won't ramble on a ton here.
It's only a matter of time until someone posts a To-Do widget on any given platform; I'm just glad Labpixies got to it first. While I'm a big fan of the widget, I did having trouble getting it to save my list. I'm not sure what the problem was, but after messing around with it for a while it seemed to work out alright.
GTD fans may also want to consider the more simple Google To Do List or My Listy