Today Khan Academy features over 2,100 videos and 100 self-paced exercises and assessments covering everything from arithmetic to math, science, history and much more; making education more accessible to anyone who wants to learn from anywhere using a Web browser and all is available for free. Not only you are going to learn great stuff, but registering for free in the site will also give the ability to practice with really cool tools and track your progress, and you always can help others too.
The Khan Academy team “is on a mission to deliver a world-class education to anyone anywhere, and you can help. Take a second to get the word out, or read about how teachers, translators, donors, and everyone else can contribute.”
If you are interesting in this project you may consider helping by spreading the word around, couch, participate in Khan Academy public groups or you can make a donation; all the information you need is right here!
When learning is one of your passions, you know that there is not such a thing as, I have enough knowledge, you know that there is always something new to learn.
Source Khan Academy