Royalty free stock photos are available from several sources including 123rf.com. A few months ago a long-time friend who is a Web designer told me about the site.
If you shoot large format, high-resolution images and would like to submit them, visit the site and read all of the requirements. They're quite selective in what they will include in their inventory, e.g. I've submitted photos that were rejected - even though I thought that they were great shots (and they were) but after I had cropped them, the resulting file sizes no longer met their criteria as they were too small. I've been uploading photos to the site for awhile by FTP. I'm starting to get the hang of it.
If you shoot great pictures and would like to share them with the world, this might be of interest to you. Here's a peek at a few of the images I've submitted that have been accepted...double-click on any of them to see the complete image in a larger version.