The governors of 11 western states have gotten together on an intiative to create a virtual university to deal with the increased demand on their state systems of postsecondary education. They plan to have the virtual university operating by this June. Some virtual universities are really just organizations that coordinate with traditional universities to help them offer some of their courses online. For example, The Electronic University Network says they offer 300 courses from a variety of accredited colleges. They have a pretty good web site that enables you to see all the courses they offer by subject area or by university.
Some subjects are clearly better candidates for distance learning than others.
The range of subjects are being taught through distance learning, however, is quite large.