Maybe you've just made your way back inside from the rain and your jacket is soaking. Or you've hand-washed your shirt after dropping sauce on it. Or you've just returned from a quick dip in the swimming pool.
Laundry
You were supposed to take the dirty clothes out to be washed days ago, but haven't got around to it. Your laundry hamper (or bathroom floor) is now overflowing with clothes.
Maybe you got distracted by the latest episode of Desperate Housewives and the bath overflowed. Or maybe your dishwasher hose sprung a leak whilst you were at work. Some reasons for flooding the house are preventable, some aren't.