Sparrow - Has different drop zones for different ways to attach files.
Google Images – When dragging a photo on the page or into the browser, the search input changes to support drag’and’drop.
Tumblr - When the number of tags exceeds the width of the post in the dashboard, a horizontal move cursor appears and the list can be dragged to reveal the rest of the tags.
Twitter for iPad - Swiping your timeline to the right, removes the content layer. It’s visualized by a little animation behind the timeline.
Chrome - Drag the little globe from the Google Chrome address bar to another browser to open the page in that browser.
/via Carlos Arellano
Offcial Twitter app for iPhone - Dragging down the whitespace of reply screen shows what tweet you are about to send reply.