The one above is when I was helping someone with connections. We had to disconnect all these wires, disconnect the box, thread everything out of the lectern they were in, then reverse all the steps with the brand-new lectern. I captured this so we would remember which order the colors connect to the box.
A couple of weeks later I was on a walk-through of an office area under construction. Rather than jot down lots of network jack numbers, I snapped a few of these so that I could send the info to someone later. This one had the advantage of reminding me where in the room it was (next to the light switch).
I don't typically keep these around after the task is finished, although a few end up tweaked into documentation (such as our how-to on using the buil-in audio-visual features in the conference rooms).
Go check out Carmi's post and see what others contributed this week.