Proof.ink - Proven immutable data stored on the Steem blockchain

EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.

Quick Freeze - Move faster by skipping the setup and management of local databases and direct integrations.

Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.

HeyForm - Paperless data collection with better data insights

Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.