Meetingbird for Gmail - View your calendar and schedule meetings right from Gmail

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

Kin Calendar - The simple and connected calendar

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

Calendly for Chrome - Schedule meetings without leaving your inbox

Strikethru - Strikethru is a kind of to-do list notebook for managing work lists and staying updated with the important tasks.