we are very lucky and have a separate room off the lounge which is DDs toy room,shehas ALL her toys in there, none in her room or anywhere else...well outside toys out side, but thats it. they come out to where ever we are playing with them, sometime the lounge room,the kitchen table, outside etc but they go back to the toy room after.
when i was a child all our toys were kept in the bedroom, and bought out to play with but put away after, ithink thats a pretty fair rule.
in our old house we had one of those playpens, as it was a highset house and dd was crawling/learning to walk, and all her toys went into the play pen when they werent being used, the pen was inthe lounge room, kinda kept them all together!