A reader named Miranda (who, sadly, recently lost her camera on a trip) sent along a link to the terrific blog Found Cameras and Orphaned Photos. The concept, as you might imagine, is pretty simple: people who find cameras or memory cards email photos to the blog, and the photos get posted. If you’ve lost your camera (or if you recognize anybody in the photos), you can contact the finder through the blog to get your photos back.
I might have done the implementation differently (enabling people to search a database by location, date lost, etc), but it’s a good start. The site will become more invaluable once photo-matching and recognition technology becomes more available.
DarrenBarefoot.com 
Of course, the best thing would be to have an identifying label, name, or personal URL on the camera or memory card in case you lose it.
Speaking of which, I should put one of those on mine…
If you lost your photos, how is photo-matching technology going to help you? You probably won’t have the original photos to work with.
The site definitely needs a database of locations though.
I good tip I heard a while ago (similar to what Derek recommends) is to write your contact info on a piece of paper, and take a photo of it, always leaving that photo on your memory card. For example, “If found, please contact …”
Of course, like many forms of “insurance” (backing up computer data, writing a will, etc.), I have yet to implement this myself!
Thanks, Darren! Much appreciated.
@Brent & Derek: Both excellent ideas. Thanks!
PS: please do go take a peep at the site in case you recognize anybody… Matt updates it with a few new pictures every Thursday. Cheers!
Parker: Presumably you would have taken photos of your self, or some other human known to you. Using a photo of a person also among the lost photos, the tech ought to be able to match them.