Step By Step Guide to Integrate Gadgets in your Gmail Sidebar
Activate the Custom Gadgets in Labs
To start using this amazing feature, you have to first enable the service. To do that, go to Settings –> Labs and enable “Add any gadget by URL” which you will find in the bottom of Gmail window and click "save changes".How to add Gadgets
Click on Gadgets tab, and enter the gadget's URL into "Add a gadget by its URL" and click "Add" button.
List of some cool Gadgets for your Gmail Inbox
FaceBook Gadget URL http://hosting.gmodules.com/ig/gadgets/file/104971404861070329537/facebook.xml



Also see - How to Use Google Search More EffectivelyÂ
After adding all these cool gadgets on Gmail sidebar, I don't have to toggle between different sites to check out all of my profiles. Now I can check my friends latest updates right from my power-packed Gmail.