Hymnal.Net Gadget for Gmail
Enter the Gmail Lab by clicking on Settings and then the Labs link.
Enable the "Add any gadget by URL" feature:
You'll see that the Gadgets tab has been added to your Gmail Settings:
Go to the Gadgets tab and enter the following URL:http://www.hymnal.net/widgets/gmailgadget.xml
The gadget is now added to your Gadgets list and you can use it from the left sidebar on your Gmail.