I've been hearing chatter throughout the industry on a new social sharing site, specifically for photos named Pinterest.
A Cre8asite Forum thread has webmasters and SEOs claiming it send a nice number of traffic, when you are featured well on the site. I've personally have not seen much traffic from it, but some sites claim as high as 900 unique visits in a single day - and the site is still in an invite only beta.
One person said:
Yep, had some. Busiest day saw around 900 visits. Been playing with it for a week or two now, interesting to see what sort of images work best.
The SEOs have their sites on this service, it better be careful now.
To see which images of yours were posted to the service, you can do something like this: pinterest.com/source/seroundtable.com/ and replace seroundtable.com with your domain.
For more on this service, see pinterest.com/about.
Forum discussion at Cre8asite Forums.