[Cacti]

It's a great program but if you can find a local one at a good school, it's still better to do it in person. Meeting faculty (and other students, researchers, doctoral or postdoc, etc) in a field you want to pursue for a long time and working on research with them is the main benefit of a graduate degree and is still invaluable. They will provide all sorts of guidance and opportunities over the years that you can't get online.