There are many colleges that now offer their courses online for free to the public. The type of courses they offer vary per school, but searching around enough you will most likely find courses on a vast range of topics. The first college I’d like to mention is MIT. MIT offers many courses on many subjects like, Engineering, Humanities & Art, Management, and Science. You can view them and try them out here: http://ocw.mit.edu/OcwWeb/web/home/home/index.htm.
The next school that offers many good courses is Yale. Yale also offers a broad range of courses, I particularly enjoy the Psychology courses. You can check out Yale’s courses here: http://oyc.yale.edu/
One of my other favorites is the University of California at Berkeley, they have Chemistry courses, Physics, Computer Science, and various other courses.