The use of open-access resources is a growing trend in education. Open Educational Resources (OER) include any teaching material (i.e. syllabi, lesson plans, worksheets, videos, games, readings, textbooks, applications, etc.) that is available free of charge to anyone with permission to reuse, revise or redistribute.
I have been using an OER as the textbook in my General Psychology face-to-face classes for 5 years, and when I started teaching on-line just over a year ago, it seemed a natural fit to continue using the same resource.