This site seems to be the granddaddy of all health information websites. I think I've seen this site referenced in just about every other health related site that I have gone to. Look at their index and you will find thousands of individual entries on everything from ADHD to Youth Violence
I decided to have a look at the ADHD entry, since it was near the top of their index page and since ADHD is something every teacher needs to deal with at some time. I found a link to a complete resource center for ADHD information (http://www.help4adhd.org/) which is funded partially by the CDC. When I clicked through the link it looked like a pretty comprehensive resource for learning about ADHD. The information that was on the CDC site itself about ADHD seemed oriented more towards research information. For instance, there was a link to list of about a dozen journal articles on ADHD. I noticed when journals were available on line (which is more the exception than the rule), there would be a link to the on line journal entry as well. There was also an extensive research agenda page which listed a large number of areas where further research could be beneficial.
I also had a look at their entry on shingles. I got this a couple of years ago, and I spent a fair amount of time studying up about it on the web. The CDC article on shingles was fairly short, but it hit all of the most important points about the disease.
Aside from the index, there are also several key topic areas like
"Diseases and Conditions", "Health Promotion", and "Traveler's
Health." I followed the "Diseases and Conditions" link down to
"Asthma." It had a nice top level overview, but not really as
much detail as I would like to see about treatments and such. My
father had asthma his whole life, and the treatments he underwent were
pretty damaging. I guess I would have to go to a different
website to get more information about better treatments.
My wife and I have checked the CDC site on occasion to find out what immunizations are recommended when we travel overseas, because the CDC is the definitive site for travel cautions. One thing I don't like about their travel cautions is they don't really give you a good feeling for the risk levels. For instance, they will label a region as a malaria danger, but you don't really have a way of gaging how great the danger really is and whether, for a short trip for instance, it is really worth it to bother with malaria drugs - which can have some unpleasant side effects.
I would recommend the CDC site as a good starting place for anyone
who wanted just about any kind of health information. However, if
you really wanted as much information as possible on one topic, I would
suggest supplementing a visit to the CDC site with a Google search to
find specialized sites on the topic in question.