It was the appliance garage in the kitchen. You know...you reach in and take appliances out of there practically every day, but you don't look inside because the space is fairly small and dark (at least ours is.) By the time you notice it's getting dirty, you (I) say "I'll get that later."
Tuesday was the day I pulled everything out of the area, grabbed the 409 and paper towels and went after it.
I have another grungy, hidden area identified to tackle next week.
What grungy areas do you have in your house?