I’ve been waiting for this feature from Google for a long time. Yeah, the other lab features such the forgotten attachment detector are fine, but this newly rolled out feature should have been implemented years ago. I guess it’s better late than never though. All you need to do is drag and drop your prospective files from one window to the e-mail and you’re good to go!
Unfortunately it only works with Firefox and Google Chrome. Find more info about it at Google’s Blog.
And I KNOW ya’ll like signature I have ;-) It's courtesy of WiseStamp, a Firefox Add on. It adds HTML signatures to e-mail services such as Gmail, Thunderbird and Hotmail/Windows Live. My less formal signature features my Xbox 360 Avatar.