I've had a few pictures licensed in relatively interesting ways. First are those stories, then a selction from my Flickr collection.
USPS ad campaign
I took this picture of my kids in 2006, while we were decorating for Christmas.
Eight months later, someone from an ad agency representing the US Postal Service called me up and asked if they could use it in a very large ad campaign for the USPS' holiday season. They'd seen it on Flickr. We negotiated a price, and for a few weeks in November and December 2007, it was really great to see Wilson and Elliot in USA Today, on the USPS website, and in mailers sent all over the country.
This photo was taken in Shenandoah National Park in the summer of 2006. Years later, Subaru licensed it for posters and other materials to be used in their dealerships.
My wife and I were looking at Subarus in August 2012 when we saw it in a dealership in Cherry Hill, NJ.