U.S. Department of Health and Human Services http://hhs.gov 
U.S. Department of State http://travel.state.gov 
Center for Disease Control and Prevention http://www2a.cdc.gov/TCEOnline 
USA Learning http://golearn.gov 
World Health Organization http://who.int 
Nurse.com http://ce.nurse.com/FreeCE.aspx 
MyFreeCE http://myfreece.com