This post is meant to keep on evolving. Here will be regular updates of the findings about 30 day challenges.
Still looking for a challenge idea?
Try these links
Ideas to change your habits: http://highexistence.com/30-challenges-for-30-days/
Learn a new skill by following free courses: http://www.Edx.com (we recommend you find a 30 lessons course, one lesson per day)
Do a meaningful action everyday: http://www.actionforhappiness.org/calendars
100 ideas of 30 day challenges https://thoughtbrick.com/lifestyle/hundred-30-day-challenge-ideas/