This is a simply terrific site for finding information about specific diseases or medical conditions. If you have gotten a particular diagnosis from a doctor and you want to learn more about what the diagnosis means, I think this is the first place you would want to go.
For instance, I looked into "depression" on this site, because I know someone who suffers from this condition, and because it is a broad topic where I would expect a lot of information. The entry on depression contained 11 separate sub-sections, including signs and symptoms, treatment, coping skills, etc. Each sub-section was around 2 or 3 pages long. In addition, there were links to other articles about medications, women and depression, etc. There was even a video titled Electroconvulsive Therapy: One Woman's Journey. Of course, there are a lot of sites devoted exclusively to mental health issues (even some devoted strictly to depression) where you can find a lot more information than this. However, unlike some more specialized sites, I feel that MayoClinic.com has a very high level of professionalism and medical authority, and I would tend to weigh information I find on other sites against what I find here. That is to say, I trust this site pretty heavily.
I also did a hunt on "shingles." I got shingles a year or two
ago and I did a lot of research on it at the time. I would say
everything I learned about shingles back then I could have found in one
entry on this site.
MayoClinic.com has a huge staff devoted to keeping it updated, and
it shows in the sheer amount of content that it contains. There
are around 50 people who are credited with creating web content, and
another 50 M.D.s who are listed as medical editors for the site
(although I suspect the M.D.s work on it on a part time basis).
One thing mayoclinic.com is not good for is self-diagnosis of medical conditions. There are some sites on the web that are aimed at that (www.webmd.com, for instance). However, I'm not so sure that self-diagnosis, even based off of a very professional website, is such a great idea. I also think this is not the best site if you are looking for generic information for good health - like the importance of eating right and getting enough exercise. There is actually a ton of information on this site about diet, fitness, and other generic health topics, but I don't think that it is organized in a way that creates an easy to follow narrative that you can read to learn healthy habits.
Another thing this site tends to lack is links to outside
sites. So far I haven't found a single link on this site to an
outside source. So, if you are looking for an index to medical
information on the web, this definitely is not it.