Those giant, free online classes offered by schools like MIT, Yale and Stanford are called Massive Open Online Courses (MOOC). Some schools are considering offering credit for these courses. Interesting read here:
http://www.nytimes.com/2012/11/14/education/moocs-to-be-evaluated-for-possible-college-credit.html?_r=0
To my knowledge, USF doesn't offer free online courses but I've seen some free audio lectures in iTunes.