WikiRadiography has many good articles, videos, tutorials, etc on radiographs and X-ray films.
This site is primarily meant for radiographers and sonographers as shown in their philosophy statement:
This site was designed to foster education, learning, development and advanced practice specifically for radiographers and sonographers. Alot of time and effort has been spent creating a site that is professional in both appearance and functionality to represent the profession in the best possible light.
Nevertheless, I think this is still a great resource not just for radiographers, but for clinicians including emergency physicians!
Click here to access.
Take a look at their article on Small Bowel Obstruction and Large Bowel Obstruction.