I have been teaching a problems-based, general oceanography course using material exclusively from online digital sources. Although much of the material is not yet in a library, it is typical of the material that is being cataloged by DLESE, the Digital Library for Earth System Education. My experiences, and the structure of the course are applicable to most geoscience courses.
The course is organized around important problems: global warming; El Nino and changing weather patterns; pollution; fisheries; and coastal erosion. Students use on-line digital material to learn about the problems, to obtain scientific information necessary to understand the problem, and to access data necessary to describe processes. There is no textbook.
Consider the first topic: global warming. There are excellent on-line tutorials describing greenhouse gases, their sources and sinks, and their influence on global surface temperature. There are also on-line data sets describing warming in various regions, the concentration of greenhouse gases in the atmosphere, and the production of greenhouse gases. Most of the information is up-to-date, complete, and well written. Furthermore, students can explore possible solutions to the problem, and the implications for society, topics usually not covered in texts. Thus, they can read the text of the Kyoto Agreement, subsequent UNESCO documents, and commentary on the Kyoto Accord by interested parties.
Students taking the course like the organization around scientific and societal problems, and the ability to access additional information quickly through the web. Some tend to be concerned that they donít have a conventional text, although they are glad to avoid the $80-$90 cost of typical oceanographic texts. Overall their evaluations of the course are very positive.
In my opinion, introductory science courses can now be taught using only digital libraries. Although I teach at the college level, the same approach has been used successfully at the high-school level.
Further information about the course, and links to digital information are at http://oceanworld.tamu.edu/ocean401/.