Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.
UpNote - A beautiful and clean cross-platform app for notes organizer
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
Notesnook - Notesnook is a simple and private note taking app that keeps your notes organized and synced on your phone, tablet and computer.
Strikethru - Strikethru is a kind of to-do list notebook for managing work lists and staying updated with the important tasks.
todoZero - A powerful to-do and note app for busy people.