There is a lot of useful information on the web, but make sure to check to make sure the source is trustworthy. It is often worthwhile to check the information from one source against another to make sure there is consistent information about a topic, lending to the credibility of the information.
A full-text archive of biomedical and life sciences journal literature at the U.S. National Institutes of Health's National Library of Medicine (NIH/NLM).