"Side Saddle Charm" by Linda Volrath
click the picture to visit the artist's website
There are lots of great resources for sidesaddle riders, such as this Equisearch article and this series of articles on NewRider.com
There are several organizations dedicated to sidesaddle horsemanship, including the American Sidesaddle Association, the United Sidesaddle Society, the International Sidesaddle Organization, and the Sidesaddle Association.
