My company posts signs on all the fridge doors of what days they will be cleaned out for the entire year. It's usually once a month, on a specific Friday. Since it's up for the entire year, people aren't really able to complain that they didn't know, since they've had to look at the sheet every day they put something in there! I'm grateful for that one, since everything else about the fridges causes a war. We have something like 4 fridges for over 200 people on my floor, and people are constantly doing things like going grocery shopping on their lunch hour and putting their groceries in the fridge, or bringing in 20 of something to last for the whole month, or trying to cram 50 huge insulated lunch bags into one fridge (which causes my stuff that's not in a reinforced lunch bag to be smashed).