Anthropology is currently 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, 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.