Lightning Calendar - Organize your life — it’s about time!
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
Google Calendar - Spend less time managing your day & more time enjoying it
Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.
Simple Calendar - A simple calendar with events (optional recurring and reminders), week numbers and a customizable...
Strikethru - Strikethru is a kind of to-do list notebook for managing work lists and staying updated with the important tasks.