If you hold down the Command key while dragging an icon to a Terminal window, it will cd to either the directory you dragged (if it's a folder) or the directory containing the item you dragged (if it's a file).
I don't know when this feature appeared; it might not be specific to 10.8, but that's where I discovered it.
[kirkmc adds: This is a really neat feature. Also, if you Command-drag an application or other bundle, Terminal will cd to inside that bundle. This is great if you need to access files within an application bundle, for example. The comments are saying that this is indeed 10.8 only.]
Mac OS X Hints