There is a new and FREE lighting diagram creator application for the iPhone and the iPod Touch called Strobox that has me pretty darn excited, but then at my age it doesn't take much.
;)
It is a great tool for jotting down your lighting setup when you are on location or in the studio.
There are a couple things I wish it would do, like edit saved diagrams or make a diagram that is larger than the existing screen (it's not scrollable) but it really doesn't bother me that I can't do these things and I doubt it will bother you.
Don't tell the developers but this is an app I would have been happy to pay for.
This really is a handy dandy tool and you should rush right over to the App Store and download Strobox now!