So I've got a circuit that runs an op amp at +15 and -15V relative to my power supply's ground. I want to use a small plug-in power supply instead of my bulky, lab one, but I can only find +15V or +30V power supplies relative to the power supply's ground. How can I get +/- 15V from a 30 V or 15V power supply? I really don't have much electronics experience so any help would be greatly appreciated! Thanks!

 

Just buy two 15 volt (isolated!) supplies and connect the -15 of one to the +15 of the other and call that connection point GROUND.

 

could I buy a +30V supply, divide voltage (with resistor) to +15V, call that ground, and then the -15V would be the negative terminal of the +30V supply?

 

yes, you can. As long as the current through the resistors is high enough that the "real" circuit you are building doesn't pull it too far off center.