You can build a wide variety of test equipment with an Arduino, and one example of this is an Inductance meter documented by Lukas Fässler. This unit is a custom-made Arduino shield containing an LCD and is easy to reproduce.
The circuit is based on a basic Colpitts Oscillator - the inductor under test causes the circuit to oscillate, the frequency of which is measured by the Arduino and then the inductance calculated.
Even if you're not interested in making your own version, the theory behind the design is quite interesting. For more information including the design files, visit Lukas' website. And for more, we're on facebook, Google+, and twitter - so follow us for news and product updates as well.