I do web development, so I offered to build some electrical calculators for their business. Spent a few days making tools for the calculations they do most often:
voltage drop and wire sizing
load calculations
conduit fill calculations
motor starting and power factor
panel schedules and service sizing
plus some residential tools for their smaller jobs
there's 24 diffrent calculators ready for use
Put everything at ElectricianCalc.com - made it work well on phones since they're usually on job sites.