Mine are in my living room of my one bedroom apartment. There is room for one in the patio closet, but then I have to open/close two more doors and get around my patio chairs (very small patio) so why bother. :-) The mountain bike frequently just lives in the car.
My cousin has hers on one of those anti-gravity type bike racks, tucked in between the kitchen table and the wall. Works well for a tight space, but you have to move the table to get a bike.