We already mentioned that the recent Gmail revamp includes new keyboard shortcuts, but this one deserves an individual shout: when you're viewing a Gmail message, you can archive it AND move to the next or previous message in one keystroke. Use the square brackets: * [ to archive and go to the previous message * ] to archive and go to the next message. Alternately, you can press y, then o to archive a message and go to the next one. You must have the keyboard shortcuts enabled in your account (visit Settings to do so) for this to work.Keyboard Shortcuts [Gmail Help]
Gmail: Gmail's Best New Keyboard Shortcut