Despite English is the most important language, Chinese is the most talked since there are so many Chinese persons on earth.For a lot of languages they have created a website where you can learn heaps of languages for free having fun, the website name is " duolingo" I recommend this website also to kids and I suggest their parents let them playing with it. You need to create an account and LEARN, ' a bit every days is the motto'
Other Resources listed here :
Rosetta stone is an important and expensive software some people find it useful some other people not, it is available on mac and win platform and there are more than 25 languages available, the approach is throughout different kind of computer exercises.
Pimsleur approach is a language course entirely audio, I recommend it while driving or simple relaxing , the approach is to put into your mind the language by repeating lots of times the sentences