@Flyback
I think you really need to define the problem a bit better. AC current, DC current, resolution, Max voltage, accuracy, distance, interference sources, where will the sensor be placed, frequency, RMS?, permissible voltage drop, 4-wire, 2-wire, etc.
In any event, I would seriously look at the Hall effect Current sensors from Allegro. There are also a number of IC's designed to measure current on the high side via a sense amp, but without any boundaries at all, it becomes an exercise in futility.