This is not meant to be an extensive list of health related resources on the Internet. These are some general starting points. There are more specific pages for Cancer links, Diabetes links, and HIV/AIDs links.
Also there is a page for Texas medical links
If you want a different list of starting points, there is the Medical Library Association's General Medical webpages. It has more sites listed and there are others pages from the Medical Library association about more specific medical areas.
Medem
This site has information from several medical societies, including the American Medical Association, and the American Psychiatric Association. The information is well presented and the design of the page is good. There is a search option but it is a basic one. There are services here for doctors too.
Mayo Clinic
The information about diseases and conditions is excellent and often includes links to other pages about the diseases. There is a drug information section I think the pages are very well laid out and easy to read. There is a search engine on the page.
Healthfinder
This page has links to health databases, medical journals, and a collection of links to other resources. There are also links to resources about health fraud on the page. The page is well organized and there is an advanced search option.
There is a section of information in Spanish.
Kidshealth.org
This page has sections for parents, children, and teens. The page(s) is (are) easy to use and well designed. There are some articles in Spanish but not many. The parents' section has information about visits to the doctor, children's growth and development, and also a section on pregnancy and newborn babies.
This site is a partner of familydoctor.org, the website of the American Academy of Family Physicans. I think that site might also be worth visiting.