Wikipedia and concept of wikis revolutionized amount of quality knowledge available online. There are many wikis which concentrate on health based topics, some of them are written for patients and others for clinicians. This page lists available online resources. This list will be continuously updated.
Medicine and related : Diabetes wiki at wikia, ECGpedia - wiki about ECG.
General practice or family practice related : Ganfyd
Radiology related : Radiopedia
Cancer related : WikiCancer
Surgery related : Sages surgical wiki
General : AskDrWiki,