Most people don't have access to academic databases so free health information is really important.These sites have reliable information and don't require a login.
Information from the National Library of Medicine aimed at patients and their families. Almost certainly has information on your chosen health condition.
Information on health conditions from the CDC. This includes information for a general audience as well as more detailed statistics and public health information.
Health information for the general public from a Canadian government agency. Covers common health conditions.
Commercial Websites
These websites also have some good information. If you use them, remember that they're operated for a profit and the ads need to be considered separately.
Along with information about their offices and programs, the Mayo Clinic produces guides to health conditions written for a general audience. (It's easier to find the full guides using the A-Z list than the site search.)