hspice vco
I used to think this was weird also, but now I look at it like this:
the inductor/capacitor form a tank circuit... and it is very literally that, a tank that stores. This is what allows it to get above the supply voltage, storage. So lets say that you store some amount during one cycle, then next cycle, because your gain is greater than one, you have all the energy you had previously, plus a little more. And so on, and so on. It is only the resistive and nonlinear part of the circuit that ends up limiting this amplitude.
There are other circuits called "pump" circuits that use a somewhat similar method of getting "dc" voltages above the supply. They pump a current onto a capacitor then switch it to add to the supply. As long as it is driving a large impedance (i.e. a capacitive load) then it isn't really supplying much current and the power lost is minimal.
Hope this helps. The above explanation was also good.