We’ve always been able to drag and drop files into a Mail message to create an attachment for that email.
I recently found out that you can actually just drag that file directly onto the Mail application and it will create a new message with that file already attached. Saves you a couple steps and you get a few seconds back. I’m not sure if this is a new feature in 10.8, it could very well have been around since 10.0…
These accidental discoveries are fun, aren’t they? Any others you can think of? Email me!