eMedicine is the largest online clinical knowledge base which has articles on over 7000 diseases and disorders, each of which undergo four levels of peer review and are consequently well written and up to date. There are hundreds of articles on every speciality. The articles cover aetiology, presentation and management. Radiology images are not found in all the articles, and in those that do contain them they are quite small (if you subscribe to the site for $19.95/year the full size images can be viewed). This site is an excellent resource for obtaining information on a wide variety of conditions, and may be particularly useful for trainees preparing for Fellowship examinations.
This site aimed at trainees offer excellent lectures, quizzes and case of the day.
Aunt Minnie offers among other things a fantastic case of the day section with is useful for testing knowledge especially prior to the part 2B exam.
If you have any other websites you feel are missing from this list then please contact us so that we can add them to the list.