http://www.vhlab.umn.edu/atlas/echocardiography-tutorial/what-is-echocardiography.shtml
This site, developed by the University of Minnesota, provides flash based tutorials on both echocardiography and cardiac MRI. Text based versions of the tutorials are also available for quick reference. The site details most of the major anatomical structures of the heart and displays their location clearly on a 3D cardiac model.