I came through a wonderful book "Teach Beyond Your Reach: An Instructor's Guide to Developing and Running Successful Distance Learning Classes, Workshops, Training Sessions and More" by Robin Neidorf.

http://www.amazon.com/Teach-Beyond-Your-Reach-Instructors/dp/0910965730

The author looks at distance learning and learning in general from many unexpected perspectives. The book goes through the full spectrum of "tools of the trade" for distance learning (from snail mail through email through videoconferencing to web-based courses), and shows unique advantages and challenges with each, what works and what doesn't and why. There is a discussion about students' learning styles and expectations towards the course, how generational differences can influence learning experience, and how to design learning activities to
appeal to different kinds of learners.