In order of increasing sophistication; cost; preparation time and presumably also in increasing learning value
Note "Low-end" can be best solution in a case where curricula material is changing rapidly
Note Open University in England (best known distance education organization uses high-end asynchronous material and for this reason cannot quickly switch to Java for introductory CS course)
"Low-end" typified by simple HTML and PowerPoint. Of course hand written notes and postscript are even less sophisticated but these are getting less important.
"Enhanced Low-end" typified by audio or video over web pages. Not clear how editing is possible/desirable
This can be viewed as a pragmatic way of capturing details from the busy lecturer who does not have the time to carefully prepare a more sophisticated resource.