There is a new cool app for the Apple iPhone that let’s you make and later share lighting diagrams for off camera lighting, it’s called STROBOX. You can get it directly from the iTunes store by hitting the link.
I, myself have only briefly tested it but it seems that almost everything is in there. There are some special lighting modifiers that can not be found (e.g. ringlight on camera like) but most is in. Hey, it’s free anyway. So give it a try!
4 Stars from me!