Simply select the folder in the explorer view, left-click, and drag it over to the Places list. Alternatively, right-click in the Places list and select “Add current folder.” You can rename the new shortcut by right-clicking on it and selecting Properties.
If you don’t like your changes, right-click on the icon and select Remove, or “Restore Standard Folders” to put it back to normal.
This doesn’t affect any other programs – actually it doesn’t appear to work at all in any other programs, which is too bad. If you know of an exception, send it on in.