These are a few resources I have found on the internet which contain authoritative information and which I have found useful. I have organized them by topic into several brief pathfinders.
General Reference | Health and Medicine | Philosophy
General Reference
CIA World Factbook – Information on countries around the world compiled by the United States Central Intelligence agency updated in part weekly
Encyclopedia Britannica – General purpose encyclopedia
Etymonline – Online dictionary of Etymology
Merriam-Webster – Dictionary and thesaurus
Wikipedia – Online crowd sourced encyclopedia with a formidable number of articles
Health and Medicine
Crazy Meds – Patient oriented information about psychiatric and neurological drugs curated by Jerod Poore
Drug Information Portal – A gateway to drug information provided by the National Library of Medicine, allows free searching of a variety of individual sources
Mayo Clinic Health Information – General health information website covering diseases and conditions as well as healthy living operated by the Mayo Clinic
MedlinePlus – Health information provided by the National Library of Medicine
National Guideline Clearinghouse – Hosts a substantial collection of evidence based medicine derived practice guidelines and treatment algorithms
PubMed – Citation database covering Medline resources as well as other resources with some links to full text documents
Quackwatch – Website covering dubious medical treatments and the hazards they present covering many areas
Philosophy
Dictionary of Philosophy – Online dictionary of philosophical terms
Open Access Philosophy Journals – Listing of philosophy journals in the Directory of Open Access Journals
Meta Encyclopedia of Philosophy – Tool for comparing entries across online encyclopedia of philosophy
Stanford Encyclopedia of Philosophy – General purpose online encyclopedia of philosophy and philosophers written by named scholars