University of New England offers several on-line versions of prereq classes that are geared towards premed/prevet/dental types (Chemistry, biochem, biology....), and since they have their own medical school, I can't imagine how these classes would not be legit. University of Nebraska also offers several online physics classes, both calculus-based and not.
I come from a state where there aren't several universities to choose from, and for many of us who live off the road system, there are no other options but to look on-line. Also, for the non-trad types that cannot take a three day a week/middle of the day class, I would think distance learning would be a workable option, as long as some classes are taken the traditional route to show you aren't just antisocial.
Taking some on-line classes can also be spun as the student isn't afraid to embrace technology, an important skill when much of medicine is telehealth/computerized....