Online Case Book by Yale School of Medicine

The Case Book by the Yale University School of Medicine covers several areas:

Doctor Patient Encounter > Interview Skills Cases
Internal Medicine Clerkship
Modules > Renal Cases
Primary Care Clerkship > Cardiothoracic cases
Surgery Clerkship

The Internal Medicine Cases are most well developed but since they are clearly written for teaching purposes during the rotation, there are only questions but no answers. The cardiothoracic cases provide both.

Image source: Case Book by Yale University School of Medicine.