If you're a gmail user you've now got some new functionality. Undo Send (when enabled) gives you a popup for 5 seconds before it sends the email, theoretically giving you time to prevent your email from being sent with a typo or missing attachement.
Yawn.
CNN is so smitten with this feature and other gmail trivia like "Mail Goggles" (to help users stop
Gmail's 5 second Undo Send. (yawn)