This is a really awesome link to a GeoGebra applet that allows you to move around the vertices of the triangle and see how that effects the circle: http://www.math.uh.edu/~jmorgan/Rice/Feuerbach/index.html
and here's another one: http://paulscottinfo.ipage.com/PLC/2/npc-java.htm
Here's a couple videos on the construction of the nine point circle:
and here's another one: http://paulscottinfo.ipage.com/PLC/2/npc-java.htm
Here's a couple videos on the construction of the nine point circle:
This video constructs the nine point circle and also shows the math behind the points using complex numbers.