FindA Doc

Long established website, since 1992 with over 1.5 million doctors, dentists and chiropractors in USA and Canada as well as over 15,000 hospitals and clinics in USA and worldwide. Also with multiple unique innovative additions including DocLINK (secure interctive Doc to Doc link) and eScheduler (personal calendars to advertize last minute patient cancellations)
https://www.findadoc.com/