Have you ever sent an email that only seconds later you wish you hadn't? Sending an embarrassing message to the wrong person with the same first name can happen without warning too. Thankfully, hitting the send button, and the feeling of panic almost happen simultaneously.
Gmail now lets you "undo" a sent message with one of their newest Labs features. Enable the feature by clicking on the labs icon at the top of your Gmail (beside settings), and click the "enable" option beside the "Undo Send" experiment.
After enabling this feature, you will notice an "undo" link above your inbox for 5 seconds after sending a message -- that might not be enough time in some situations, but it's better than nothing!
In addition to this feature, there were also some other new experiments that may interest you -- they include inline YouTube, Picasa, Flicker, and Yelp previews. What do you think of these new features?