Our house is on the market and had a call from agent saying someone wanted to view at lunchtime the other day, but with going to work that left me with an hour to clean.
As a matter of interest, just wondering what others would do. Luckily I was in the middle of cleaning the bathroom, opened windows to freshen up (as I always do before a viewing), hovered downstairs only, did washing up, put away and wiped around that area and put cat's litter tray out. Luckily I've been trying to keep on top of dusting between viewings, but didn't really have time to tidy piles up, stuff things in cupboards and hover upstairs!
When I have to do a panic tidy up I do the things that most obviously need doing, like any dishes, bathroom etc and spend the last ten minutes picking up any piles of crap odds and ends, shoving them in bags and hiding bags in wardrobes etc.