I have really grown to love what the NIH/National Library of Medicine are doing here at MedlinePlus: Drugs, Herbs and Supplement sections.
When I am not using it to check trade names/generic names I really like to search various drugs that come up in our study and check out the side effects. e.g: “foamy urine” (this would be totally terrifying even before i contemplated what it was communicating to me about my kidneys). Or, you know, check to see whether or not my symptoms that come with taking over the recommending dosage of various OTC allergy/cold meds are worth paying any attention to.
