Going back to school...often a "resolution" for the New Year. Several free sites exist, all well know and well respected exist where we can all go to improve our knowledge. While you won't get a degree from these sites, you can get a certificate of completion. I for one am not necessarily a "Certificate collector" and value the information much more.
Here are three site I am aware of:
MIT online: http://ocw.mit.edu/index.htm
Yale online: http://oyc.yale.edu/
Kahn Academy: http://www.khanacademy.org/