Here's what we do: The kids are responsible for all "their" areas (bedrooms, toys, their shared bathroom, putting away their own laundry, and sometimes kitchen help). Any other areas--vacuuming the main rooms, guest bathrooms, outdoor yard work (picking up sticks, etc.) can be done for money, but ONLY if they are doing the "take care of your own area" things. The money-making chores are optional for now. I will say, however, that this is sporadic in its efficacy. Mine are still young--the youngest is 5--so maybe it will work for older kids better. ;-)
Hope that gives you some ideas!