New features in Gmail seem to be a dime a dozen lately, from drunk email protection through to viewing YouTube videos inline. Some of the features rolled out in Gmail Labs have been useful before, but none perhaps as useful as the latest: "Forgotten Attachment Detector."
The Forgotten Attachment Detector uses the same technology behind Google's ad platform to detect whether you've mentioned in your email that you were going to add an attachment. If you hit send without having set up an attachment, you receive a pop up that asks if you meant to add an attachment or not. If you haven't mentioned an attachment in your email, you simply don't get the box, and it's business as usual.
Maybe not everyone occasionally forgets to add an attachment to an email, but I'd bet many do. I unfortunately do it regularly, getting carried away with the email then forgetting to add the relevant attachment. As a pure and simple value add this is brilliant and a step that will save me on a regular basis.
To switch on Forgotten Attachment Detector, go to Settings/ Labs then scroll down the page to find the option.