I've been taking pictures since I was a kid and while I did supplement my income a bit while in school taking photos of hockey games and snow statues and selling them to the university as well as taking senior pictures for the yearbook, the extent of their publication was limited. However for the past year or so I've been uploading photos to a stock-photo house in the UK which acts as a broker selling stock photos to publications, the media, organizations that need images for whatever purpose, etc. Over the last few month three of my photos have been sold, and I just received my first payment, a total of $55 (I get half of what the broker sells the images for). Now the copyright and ownership of the images are retained by me as the company is merely acting my 'broker' helping to facilitate the sales.
Now the amount I get paid depends on the size of the image sold and how the image is going to be used. I don't know who purchases them nor what the actual usage is going to be nor where they will appear, just the amount of the sale, the size of image provided to the buyer and whether it was for one-time usage or not.
Here are the images that have been purchased so far:

This is the Copper Harbor lighthouse on the shore of Lake Superior in Michigan's Upper Peninsula taken in August 2008 with a Sony A100 DSLR, and it sold for $50 as a medium-sized, one-time usage.

This is a shot of my alma mater's campus, Michigan Technological University, in Houghton located in Michigan's Upper Peninsula, also taken in August 2008 with a Sony A100 DSLR, and it sold for $10 as a thumbnail image, one-time usage.

This is a shot of the main entrance to the Olympic Coliseum in Los Angeles taken in December 2013 with a Sony A65 DSLR, and it sold for $50 as a medium-sized, one-time usage.
Now it's obvious that I'll probably not make a living selling photos this way, but it is fun and who knows, if I manage to sell enough of them to make it more than a hobby, I might be able to recover the cost of some of my camera gear.

OCU