For true learners that crave for retention exercises while studying, Coursera is the place!

Coursera (https://www.coursera.org/courses) has almost become my marketplace of choice for testing my interests in areas alien to me. The difference between Coursera and a passive medium like iTunes University is that the courses are interactive. You are asked to submit home works and can evaluate the home works of other fellow students. I really like the frequent feedback that they provide, which helps you to monitor your own progress, and know when you've really mastered the material.Coursera offers courses in a wide range of topics: From topics that appeal to people who want a better society such as Humanities, Social Sciences, Medicine;  to topics for the mathematically inclined folks in areas such as Biology, Mathematics, Business, and Computer Science. The courses are free and in some cases they come with an ability to donate to pay for the environment. The courses are offered by faculty at world class universities making it a truly immersive environment. Try before you buy never has been better. For some courses, you can even earn a certificate should you satisfactorily complete the coursework. Great site. My favorite. Enjoy!