I'm just finishing up Andrew Ng's Machine Learning course and would definitely say it's worth it (depending on how much, if anything, you already know about ML).

I'm also about halfway through the Johns Hopkins Data Science specialization, and I've found all of those courses to be worthwhile. But then again, I'd never programmed in R before and that's something I very pointedly wanted to pick up. So far, this series has been invaluable in terms of learning R (much like I had to learn a fair amount of Octave for Andrew Ng's class).

I've taken Andrew Ng's class and thought it was fabulous despite having extensive prior ML knowledge. I'm currently taking a negotiation class by Yale university which is very valuable do far and already has changed how I think about deal making. My wife just finished a script writing class and also got great value out of it despite being an accomplished writer.