Anthropology is an exciting field for open access publishing. Together with colleagues from around the world we have developed the Open Encyclopedia of Anthropology (OEA). You can find it here: www.anthroencyclopedia.com. After serving as its co-founder and Managing Editor for 6 years, I now serve as the OEA's publisher and style editor, through the NGO Open Knowledge Press.
Colleagues at the University of Edinburgh and I incorporated Wikipedia into teaching. Our aim was to train students on how to edit this free encyclopedia and to make a certain amount of mandatory edits part of their course. This provides them with first-hand insights into the nature of online publishing, including its checks and balances on knowledge production. You can find a how-to-guide and a brief assessment of using Wikipedia editing as part of teaching here.