Yesterday the Gmail Blog posted Drag and drop attachments to save them to your desktop … for now it looks like it may only be available on Chrome.
Dragging and dropping files is an easy way to save time in Gmail. We’ve previously blogged about dragging files to upload as attachments and dragging images into new messages. Now, if you’re using Google Chrome, you can also drag attachments out of messages you receive to save them to your computer.
– Gmail Blog