Shared To-Do List with Contractor

[Steve Sorensen]

Looking for recommendations for an app or other software to track remaining to-do items in a shared list. I want something simple (and ideally free) that we can both download and update as tasks are completed. I've found a few general suggestions online, wondering if anyone has experience with a reliable app. These are simple SFH remodels so I don't need any sort of fancy document control software.