A while back, I had a project that required high-side switching of a set of pneumatic valves by a microcontroller.

Completed board

Because the loads were inductive (solenoids) and required a good deal more voltage than the microcontroller supply to activate (24V), I needed some kind of middleware between the Arduino and the valves.  I created a board that allows for control of 8 high-side switched loads (powered by anything between 5 Volts and 60 Volts) using logic level signals, and have now published the results as the 8 Port High-V High-Side Switch project.

If you find yourself needing to feed (relatively) high voltage (and up to around 9A) to a set of loads using a microcontroller, check out the project and let me know if you have any questions, comments or success stories.  Have fun!