You can get an app that puts a live tile on your start screen that jumps to settings WIFI then you have ton tap the off slider so 2 steps. There are free and pay apps you can chose from just depends what you want to be able to turn on and off.
yup two taps once its pinned on your screen .. im patiently waiting for someone to develop a proximity wifi switch that automatically turns your wifi on when your close to home .. that would be sweet