http://www.drgdiaz.com/intro.shtml
http://ultrasound.ucsf.edu/USCases.html
http://marr.bsee.swin.edu.au/~dtl/het408/ultrasound/ultrasound.html
http://www.bcc.ctc.edu/ultrasound/
http://brighamrad.harvard.edu/education/online/US/
http://www.diagnosticultrasound.yourmd.com/