Just say what it is and let the reader decide how important it is. I say something like, Machine Learning 2011 (ml-class.org; free, online, no-credit Stanford c

Just say what it is and let the reader decide how important it is. I say something like, Machine Learning 2011 (ml-class.org; free, online, no-credit Stanford course). Though personally, if I haven't even begun a class I wouldn't mention it - what is an employer to do with that info? Perhaps you'd get a plus for taking classes but...