Pierre said:
Libraries are especially useful in a LAN environment. By default, the "save as…" dialog in most programs will open the relevant library ("Documents" for a word processor, "Pictures" for a graphic editor, etc…), and you can add any folder to a library – including a network share. This will save you some navigation.
There's only one drawback - if the share you're trying to add to a library isn't indexed on the server you won't be able to add it to the library.

