Does the school or the student cover health insurance for PhD students in the US? I was just wondering what people's experiences were regarding health insurance at US institutions for PhD candidates.  Does the school, itself, cover the cost, the individual, or something else?  I am particularly curious how this may be changing in response to the Affordable Care Act.
This varies tremendously from one university to another.  At some institutions you're on your own to buy insurance through the exchange. At other institutions the university pays for insurance for students and their families as part of the compensation for teaching/research assistants, similar to the way in which staff are insured.  It's important for students to understand exactly what is being offered as part of the TA/RA package.  

Some institutions that used to offer low cost/low benefit insurance plans to students have had to stop offering those plans because they weren't compatible with the ACA.