AppleMatters has published a great list of their top ten ways photographers can benefit from the iPhone. From sharing your portfolio on-the-go to note taking, it's a good list. My favorite is the example of a wedding photographer who keeps a sort of "check list" of shots to get (grouped shots, individual shots, etc.) as a reference on his phone.
We've seen people use the iPhone's camera to create to-do lists, share instructional videos and more. On a recent car shopping expedition, I made a gallery of all the vehicles I test drove for reference and comparison at home.
What's your favorite uncommon use of the iPhone?