10.5: Use the Get Info window’s proxy icon:

Leopard’s Finder Get Info panel now has a proxy icon on the panel’s title bar. It can be dragged like the proxy icon in a Finder window title bar, and behaves in the same manner. Dragging while holding Option-Command will create an alias. Dragging while holding Option will copy the file if the destination is on the same volume. Just dragging to a destination on the same volume will move the file.

[robg adds: You can also Control- or Command-click on the proxy icon to see the path to the chosen item. Select a spot in the path, and the Finder will open a new window showing that directory.]