The Clinical Cases and Images blog is a "free case-based curriculum of clinical medicine." I stumbled upon this resource three years ago and have recommended it as a reference to students for finding clinical images that are accompanied by helpful discussions.
The blog was created in 2005 and is a joint effort of physicians at the Cleveland Clinic and the Case Western Reserve School of Medicine. It is well organized by specialties along the top menu bar.
The topics covered include:
Allergy & Immunology -- Cardiology -- Pulmonology -- Gastroenterology -- Nephrology -- Endocrinology -- Hematology & Oncology -- Rheumatology -- Infectious Diseases -- Neuorology -- Geriatrics -- Pain Management
Other categories offered provide more information and links in the right menu bar:
-- Physical Examination Videos
-- Procedure Guides Step-by-Step
-- Electrocardiograms, X-rays, CT scans
-- Clinical Images from NEJM
-- Clinical Cases in Test Format (test your knowledge based on details of a case)
In the lower part of the right menu bar is a link to many of the images found in the blog that are housed on the photo hosting site Flickr - http://www.flickr.com/photos/clinicalcases/.
The comments made on the content are helpful discussions. An encouraging feature to note is that all entries have a "Published" and "Last Updated" dates that you'll find by scrolling down the page. This can help you evaluate the usefulness and timeliness of the content.
To get a sampling of what you can learn from this well done blog, take a look at EKGs with Dr. Koch: It's Not Only Educational It's Also Fun!