Drag and Drop Plus

Every window in Mac OS X has a title bar at the top, showing the name of what you are viewing. When you are viewing a window in the Finder, it displays title of the folder you are in and an icon next to it. You can move that icon by clicking and dragging it anywhere you wish, and it will relocate the folder.

The folder icon in the title bar can be dragged anywhere to move the entire folder

I have never found much use for this feature in the Finder. What is useful about this feature is that it doesn't apply only to the Finder. You can drag the Title bar icon in any application that supports the feature into any other application. For example, to place the example picture above into this post, I took a screenshot and edited it in the Preview application. Then, when I wanted to add the picture I dragged the Title bar icon into the dialog box asking me to select the file for upload. That looked something like this:

A window in a window: this shows a window in the application Preview, and dragging the title bar icon. 

It's useful anytime you want to move files between applications. The two caveats are that the file you want to move must be saved, and  sometimes when you drag this icon what will appear is the path to the file, not the contents of the file itself. SimpleText, for example, would show the path of my screenshot1 file, but Word would import the picture itself.

It is a feature worth playing with. It may save you a couple of steps, especially if you are editing different related files in different applications.