Free Online Learning

Here are few site links which provide on line learning for free. They distribute lectures and notes for free.
You can see lectures of your interest and increase your knowledge.

NPTEL provides E-learning through online Web and Video courses in Engineering, Science and humanities streams.
http://nptel.iitm.ac.in/

MIT OpenCourseware - contains lectures and notes provided by MIT professors.
http://ocw.mit.edu/index.htm

Coursera contains lectures provided by prof of some of the good university of US.
https://www.coursera.org

You can also find a large set of video lectures shared on you tube.
Below are few you tube links.
http://www.youtube.com/user/StanfordUniversity
http://www.youtube.com/user/Harvard
http://www.youtube.com/user/UCBerkeley
http://www.youtube.com/user/nptelhrd

Security tube- contains lectures and demo related to hacking, information security, wireless security, hacking tools etc.
http://www.securitytube.net/

videolectures.net

learnerstv.com

Khan Academy - contains teaching materials related to  mathematics, history, healthcare and medicine, finance, physics, chemistry, biology, astronomy, economics, cosmology, organic chemistry, American civics, art history, microeconomics and computer science
http://www.khanacademy.org/

Google also provides learning tutorials that are present at site mentioned below. These contains lectures, presentations, assignments shared by some US Grad College Professors and some Google employees.
http://code.google.com/edu/


itunes U

Itunes U is an application provided by apple for your your iphone, ipads, ipod touch using which allow you can download lectures and read it on your iphone, ipads, ipod. you can gain access to these lectures on your personal computers too via installing itunes on your computer.