MedNar is a federated search that covers the "deep web" of medical information, find more in-depth information than you might find with the typical website. It searches commercial sites as well as government sites, and allows for limiting results by type. MedNar also suggests medical subject headings (MeSH) for searches, as well a medical dicitonary. A good place to look when you need to do an in-depth search:
Need a definition of a medical term? Try the following:
"The A.D.A.M. Medical Encyclopedia includes over 4,000 articles about diseases, tests, symptoms, injuries, and surgeries. It also contains an extensive library of medical photographs and illustrations."
This Flash-based tutorial is aimed at health consumers rather than health professionals, but you may find it a quick refresher on medical terms.