If you are considering taking an online course or just curious about online education, you might want to check out the Online Schools Guidebook, put out by Accredited Schools Online.  And it really is like a book, since the guidebook page has the equivalent of 25 pages of information.  This includes some great material on free resources and trends.

The main page also has a searchable list of schools and programs from all over the country.  It including several ways to filter the data and generate maps of their locations.