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The Gmail factory has not stopped experimenting and neither does it plan to do any sooner. They have come up with two more apps, Tasks, Text Messaging in Chat
Tasks
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Keep track of what you need to do with a lightweight task list right inside of Gmail. Just click and type to add new tasks, convert emails into tasks, and (most satisfyingly) check them off as you're done. Once you turn on this Labs feature, look for the Tasks link to the left of your inbox under Contacts.