Can I damage an arduino by setting pins high with no load I have an Arduino project that has 15 different output pins set.  Some are currently attached to devices and others are not.  Will testing my program cause a problem / damage if it sets pints to HIGH that do not have anything connected to them?
Nope, you should be just fine.

Having a pin set to any state while unplugged will not cause any problems with your microcontroller.