Online TODO list. As a web app it works great on a mobile phone or tablet once you add it to your homescreen. Minimal, open source, fully hosted, with the option for self-hosting.

Web based. Easy to install. Self-hosted & open source. Allows multiple people to update a list. Mobile friendly - "Add to Home Screen" webapp. Simple text based format for easy editing. Simple PHP backend with no database: just upload the files and go.