Travis Jordan wrote:
If your 220v outlet is an older style and only has two hot wires and a
ground (usually red, black, and bare/green) you can't create a 110v
circuit from it. If your outlet has 2 hot wires (usually red, black),
a neutral (white), and a ground (bare/green), you can get 110v from
either of the hot wires (black or red) to neutral (white). I'd
suggest mounting a new outlet box adjacent to the current box with a
110v duplex outlet, wired as above. BE SURE TO LOCATE AND TURN OFF
THE RIGHT CIRCUIT BREAKER BEFORE YOU START.

If you don't completely understand this advice and the risks
associated with working on house circuits, don't attempt it.

I should have also mentioned that in order to be safe you should insure
that the existing 220v circuit breakers do not exceed the rating of the
new outlet - i.e. 15 or 20 amps, depending on what type of 110V outlet
you use.