The sites I use for learning languages are http://www.duolingo.com – which has a free option. Also http://www.italki.com – if you go to “community” you may be able to swap time in your language for the one you want to learn – for free.
There are also free online courses in lots of subjects with http://www.futurelearn.com
Not sure this stuff is everyone’s idea of fun – but it could get you started … I am sure you can think of other stuff!