I recently joined (late) Change MOOC and am picking up the discussion from Week 7 on Open Educational Resources. My own experience as an educator with OER is limited, though I have tried a few things: My Composition 1 class last summer used sections from the Flatworld Knowledge Guide to Writing. Check out their organization here.
Additionally, I encourage students to explore the resources shared on Google Scholar and Google Books, though I'm not sure these are entirely open, per say, since the educational institutions are not sharing them directly, but instead through a corporate entity. Maybe I'll find out the answer to that question after digging into Week 7.
Personally, I have used open source materials for creating slideshows and open source software for recording screen casts and mp3 lectures for students.
I am slowly working on a project to compile and curate all free texts and materials related to Romantic Poetry in order to build an online repository that can be used instead of, or in addition to, an expensive textbook that says Norton on it. I'm calling this project, "Old Dead White Guys Give it Away for Free." That probably won't be the final title.