http://sixrevisions.com/resources/10-puzzle-websites-to-sharpen-your-programming-skills/ http://sixrevisions.com/resources/10-puzzle-websites-to-shar... and rec

http://sixrevisions.com/resources/10-puzzle-websites-to-sharpen-your-programming-skills/ http://sixrevisions.com/resources/10-puzzle-websites-to-shar... and recently I came across dropbox challenge as well! http://www.dropbox.com/jobs/challenges http://www.dropbox.com/jobs/challenges