There are IC-like inverter modules which allow you to make anything out of anything. Look at www.dc-dc.com. They offer a very energy efficient solution, but they will give you some HF noise on your power lines.
Another way to do it is: make a single supply, use two equal resistors to make a voltage inbetween. If you need some more power from this "srtificial ground", use an op-amp voltage follower. Need even more power? use an additional transistor stage. This solution is less energy efficient, but may be cheaper and free of HF.

Hans