Massive Open Online Courses are a fantastic way of learning more for free. Many courses are offered by prestigious universities from around the world and cover school subjects as well as many more that you can't take in school. If you want to study a new subject at university, try a MOOC to find out if the subject is what you expect. If you need further skills in a particular area to improve you chances of getting into a particular profession, then a MOOC could be the answer.
There is a list of excellent resources below.
Search for free online courses at:
www.mooc.org - over 1900 courses from edX
www.open.edu - over 1000 free courses offered by the Open University covering a wide variety of topics
www.coursera.org - wide range of courses from different providers
www.udacity.com - another large scale provider of courses
www.bbc.co.uk/academy - many useful resources about journalism, media, production