I am using a program called LectriCalc 2.0.4 by Arkansoft on my Handspring Visor with Palm 3.5 OS.
It does voltage drop calculations and simple watt/amps/voltage/hp calculations. It also does a simplified footcandle calculation (with one fixture) and an energy cost calculator.
It also has a reference section with calculations for dwelling and commercial services, tables for conduit sizes, 1 and 3 phase motors.