Learn how to remove an item from the sidebar in Mac OS X v10.6.7 or later.
Mac OS X 10.6
- Press and hold the Command () key.
- Drag the item from the Finder sidebar and release it.
Note: If you don’t hold down the Command key while dragging the item, it will snap back to the sidebar when you release it.
In the image above, Applications is selected in the Finder sidebar, and is a really crummy example.
To add an item, simply drag it to the correct area. You don’t have to hold down a modifier key—such as the Command key—to drag an item into the sidebar of a Finder window.
[ This article boldly stolen from the Apple Support Database. Why? Because I had to look it up again.]