A domestic goddess refers to the common housewife, but in more contemporary and flattering terms. The domestic part comes from the obvious fact that they (the goddesses) are very home oriented and work from home to accomplish small miracles. The goddess part refers to the incredible level of multitasking these fine beings are capable of accomplishing. Who needs SMP when your mom or wife can bake cookies, clean the kitchen, prepare dinner and pick little Bobby from soccer practice. I don't know where the term originated but it seems more and more common these days. Domestic Goddesses can even bring you a beer out of the fridge. Maybe because this type of lady is rare and coveted among men is the reason they are referred to as domestic goddesses.
User FeltTips adds:
To answer the comment above about the origin of the term domestic goddess, it was originally coined by actor, director, writer, comedian, TV/radio host, producer Roseanne Barr when she was doing standup comedy in Denver, Colorado, clubs and later, on late-night television, based on being a working class multi tasking woman.