Good challenges website to learn?

I'm looking forward to learn machine learning, but I'm not very good with reading books on the subject in order to do so.

I am quite experienced with programming, and managed to learn a new language (Clojure) only by doing online programming challenges, using 4clojure.com .

I would like to know if a similar website exists, with challenges and instant feedback, do that I can learn both machine learning and data analysis.