GMail Time Management
If you read Getting Things Done by David Allen, then this extension will assist you in managing your tasks and time efficiently.
For those who don't know anything about Getting Things Done (GTD), you follow these steps in getting yourself organized:
You may not know it (you probably do), but GMail already takes care of the first category: It collects. The extension adds the following functionality to take care of the Process, Organize, and Review. The last step, Do, is up to you.
One of the features I like is the ability to view outstanding tasks quickly. You send yourself tasks and references through GMail.
This extension was extremely easy to install and reminds me of the greasemonkey extension, which if you are a developer, takes an existing web site and adds additional functionality.
The extension works beautifully and if you've read the book, Getting Things Done, it will be a great benefit in using your time and energy more wisely.