I took a Medical Terminology class from here: http://www.universalclass.com/i/crn/31935.htm, which was recommended by the PT school for which I applied and attending. It's very straightforward and easy to do. Lots of memorizing, though.
We send people to Corexcel for Medical Terminology. Here is the link for their course: http://www.corexcel.com/html/online.medical.terminology.htm. I asked my supervisor why they chose this course over others and she said it was because they offer a college credit option. Apparently it's difficult to find courses with this option.
I've also taken the Corexcel Medical Terminology course and I found it to be very good. My college accepted the credits and the process was easy. I looked at Universal Class, University of Phoenix and a few others. I don't like to sign up for recurring monthly credit card charges and I wasn't looking for an entire degree program. However, the content looked similar.