Khan Academy > Computer Science videos:  http://www.khanacademy.org/cs

Codeacademy: http://codecademy.com/

Coursera http://coursera.com/

EdX http://edx.org

Code.org http://code.org

Language-specific:

- Ruby

  http://kidsruby.com/

  http://railsforzombies.org/

  http://tryruby.org/

Challenges

https://interviewstreet.com/ (hiring for Facebook, Microsoft, Quora, Airbnb, Groupon, Spotify, Justin.TV and many others)

  Example: https://facebook.interviewstreet.com/recruit/challenges

Misc: