Favorite Mailboxes in Lion Mail - Matt Legend Gemmell →

A keyboard shortcut of Command-n is applied to each of your favorite mailboxes in sequence, with n being a number starting at 1. You can trigger the shortcut to open the corresponding mailbox (i.e. to select it in the mailboxes list, displaying its contents).

This is a good tip. Also, for those that don’t know, this works in the favorites bar of Safari as well. Been using it for years.