If you have more than one email account setup in Apple Mail.app, it's nice to be able to select the one you want to send a message from without having to use the mouse.
Here's how to do it:
The "Menu Title" field must be exactly as your account name appears in mail when you are selecting the account you want to send a message from:
"Your Name <name@place.com>"
I like Control-1 for my first account, increasing in number for each account.