[DegrawSt] uses four 50 kg load cells to create a bathroom scale using an Arduino. Load cells typically contain strain gauges that change resistance when deformed.

For those starting out in Arduino, there are tons of resources to get better acquainted with the community and the types of projects you can tinker with.

A simple Arduino project to measure the stability of USB power supplies. This project can easily be reconfigured to be a simple digital voltage meter.