Here's a fun thing to play around with, if you're bored at 3am. Most Sony digital cameras start saving photos with the following name "DSC00001.JPG" and a lot of people take these photos and upload them to the web, where the all-knowing, all-seeing Google later catalogs all of them. So by clicking this link you can see the first photo taken by someone with their new camera or newly formatted card for some cameras, this is what it looks like when thousands of Sony cameras lose their photo-virginity.
Update: Bonus fun, IMG_0001.JPG is the equivalent for Canon cameras.
So, that will work too. Here's
Nikon. And one of our readers points out "Using DSC as a search string in P2P programs also works great for turning
up things on peoples hard drives they they didnt know they were sharing".