One way might be to find a cheap 'wall wart' power module rated for 220ac input and DC output. Then you could use a simple 2 resistor voltage divider in the voltage rating is higher then 5vdc and wire that into either a digital input or even a analog input pin.
Something like this might work: http://www.allelectronics.com/make-a-store/item/PS-478/4.7-VDC-850MA-POWER-SUPPLY/1.html
Please be careful wiring around 220ac, it can be very unforgiving.
Lefty