Isolating motor control signals from microcontroller from high voltage/current lines
Opto-isolation is the way to go. I've used it for driving a high-voltage ultrasonic amplifier from an MCU waveform generator, and it's often used for motor drivers.

Filtering the MCU supply and the use of TVSs, such as AVX TransGuards, will avoid other problems arising from the proximity of high voltages and currents, as well as transients on the mains supply.