There's a big difference between flying without the power from one or more engines, versus continuing with controlled flight after the departure of an engine from the rest of the airplane. As has been reported by several posters, there have been several more or less successful outcomes to partial or total power failures.

I can't recall of a successful landing after physically losing an engine though. From what I understand, engine departure under certain circumstances is a good thing, as it is supposed to shear off and away from the aircraft without causing further damage (this is what I recall having heard in a flight test class I took too long ago). The problem is the collateral damage caused by the destruction of the engine which usually is too severe to be compensated by the aircraft or crew. I remember reading a lot about this at the time of the AA DC-10 accident in ORD. There were claims that the DC-10 design was flawed, since departure of the engine took out the ducts through which the flight control (and fuel, I believe) systems passed. Supposedly, Boeing aircraft would not be affected in the same way.

Someone with more accurate knowledge will surely be able to provide clarifications.