McGraw Hill and Unbound Medicine have just released a free differential diagnosis tool cleverly named "Diagnosaurus", adapted from CURRENT Medical Diagnosis and Treatment. The program provides access to more than 1,000 differential diagnoses, covering more than 500 symptoms and signs, and 700 diseases. Information is alphabetically categorized and searchable by disease, symptom and organ system. The symptom selections are all hyperlinked with cross-references to related diagnoses within the program. All in all, a very interesting and unique program!