Since it’s the beginning of summer and already pretty hot in the southern US where we are, the temptation is to make it a little extra cool inside to make up for the amount of heat pouring in the windows. But we gradually acclimate ourselves over the spring months (turning the thermostat up a degree at a time as the outside temperature dictates) until we can stand around 78°F inside. We keep ceiling fans on at night in bedrooms to ensure no one sleeps too hot, but otherwise it’s pretty comfortable, and saves a good amount on our power bill. Only exceptions are, again, when we have company–and we turn it down to around 76°F.
In the winter, we do the reverse–we let it get as cool as we can keep it comfortably for the kids (with a little bundling up if necessary) before we turn the heat on. I know several people in the northern US that let it get as cool as 40°F in their house! I’m not sure I could do that, being a Florida girl and all, but I’m sure it helps out with the bills! ;)