Here are two- http://www.amu.apus.edu/Academics/Degree-Programs/program.htm?progid=4465&program_type=Masters http://www.fhsu.edu/mls/conc/history.shtml
I'm not sure which of these will let you take just individual courses, but here are a few that have entire degrees by distance learning. American Military University www.apus.edu Austin Peay State University www.apsu.edu California State University Dominguez Hills www.csudh.edu Fort Hays State University www.fhsu.edu Goddard College www.goddard.edu Goucher College www.goucher.edu Norwich University www.norwich.edu Regis University www.regis.edu Sam Houston State University www.shsu.edu Savannah College of Art & Design www.scad.edu Southwestern Assemblies of God University www.sagu.edu Syracuse University www.syr.edu Union Institute & University www.tui.edu University of West Alabama www.uwa.edu Western Kentucky University www.wku.edu Western New Mexico University www.wnmu.edu
I can vouch for West Alabama. They have a good history course selection and the courses are well constructed.