Ask HN: How machine learning algorithms are helping to solve important problems?

I'm reading the book "Programming Collective Intelligence" in order to have a basic idea about ML algorithms, but the algorithms are used to solve problems like: price models, better recommendations, trip planning...

I'd like to know about interesting projects(open source would be great) that apply ML to help solving problems in fields like: health, education, nutrition, politics, agriculture...

Thank you in advance for your replies.