One of my forum buds suggested these for reliable information:
Major research/teaching hospitals (e.g., Mayo)
Major universities, especially those with AD research centers (e.g., UCSF, Johns Hopkins)
Companies that publish manuals and textbooks for physicians (the Merck Manual Medical Library springs to mind, they have excellent resources)
Major non-profit associations (e.g., the Alz Assoc, Fisher Center for Alzheimer's, AFTD, LBDA, Family Caregiver Alliance)
Professional associations (e.g., AMA and -- especially for info on AD research -- the Alzheimer Research Forum)
Magazines and journals published by professional associations (e.g., Psychiatric Times)
Government agencies (e.g., any of the National Institutes of Health, FDA, CDC)
Organizations that offer CME (continuing medical education), e.g., www.Medscape.com
Sites that have independent medical review boards to vet their articles
Science Daily is pretty good, but always read the original research papers, too.