I find my self taking photos of things that I need reminders on. If I'm walking through town and see an interesting poster in a window, I take a quick photo for a later reminder (sign up for history walks, concerts, etc).
My kids and I shoot SMS text messages back and forth a lot with great scenic photos of where we are. My daughter moved to Whistler, BC a couple months ago for work and sent me some great shots of the park at the lake near Whistler Village today. The neatest thing was our family vacation in July 2011 for my 60th. We climbed Mt. Washburn, the tallest peak in Yellowstone Park, about 10,200 ft. At the top is a Ranger Station / Fire Outlook and a cell connection. The kids snapped photos on the peak and had them on Facebook in a minute or two and were getting responses from their friends right away!
That's a great idea about shooting photos of serial numbers! I can't see the numbers on my equipment without pulling it out of the rack. I can just shove the camera behind the rack and take a pic.
I saw a cool article about a new McClaren car being introduced in 2013 in our local paper today. It doesn't have a daily web page (yuck), so I snapped a pic of the photo in the newspaper and sent it to my son who's a huge McClaren fan.
I also dictate text messages to Siri when I'm driving or walking and shoot off SMS messages that way. MUCH faster than keyboarding.
It is truly an amazing machine.