Instructables
Picture of Using a NAND or NOR gate as a NOT
Simple trick to using a NAND or NOR gate to create an Inverter or NOT gate.

If you tie one input into both inputs of the NAND or NOR gate, it will create the equivalent of a NOT gate.

This can be useful when you are already using a larger IC NAND or NOR chip and you need to throw an inverter in there.

The photo shows all three gates completing the same function