Here in the city, they don't usually last long, maybe a day or two. Either the city or some homeowner cleans them up, I'm not sure (I've buried my share of squirrels). If you're out in a more rural area, and are feeling brave, try and toss it into the woods/fields nearby. It may help keep the smell down, plus you won't have to look at it every day. If it's something big, call whatever authorities responsible for such cleanup.

Or, take ItsJustMe's advice and observe the wonders of decomposition, haha