I chose Professor and Lion's room.
The room had a peculiar odor--as anyone who has a boy with a room can attest. Stuff was jammed under the beds, cracker crumbs danced near the bookshelf and by the wall, dirty clothes lounged with everything else. It was a stew that would make an ogre proud.
It took around six hours that day and another hour or two the next (not to mention sweeping enough dirt to plant a small garden--what the heck?), but all the bags of stuff were taken downstairs, leaving the boys' wooden floor gleaming in the afternoon sunlight. They were left with a few things on the bookshelf in the closet.
Every day since then, if their room is clean, they're allowed to go downstairs and get one toy out of the bags. If anything is left on the floor it goes back downstairs. They've been very careful to keep things where they belong. The funny thing is that they're very choosy about what to get, because they don't want to mess up their room again. Having the toys gone makes the room much easier to keep clean. I never, ever thought my boys could keep their room immaculate for over a week! It feels weird even typing the word 'boys' and the word 'immaculate' in the same sentence!
The magic with this method is that the agony of deciding what to keep and what to get rid of is taken away. The kids didn't like putting everything in the bags, but the knowledge that they could take their favorite things back out made it far easier. When they're done taking what they want, the bags will be gone through a final time by me and donated/thrown out.
A word of caution: be very careful what you promise. The day after this happened, Lion proclaimed "Hooray! Now all we have to do is keep it clean for 30 days and then we earn Mario Party 8!" A dim memory floated to the surface of my mind like a bubble that has been trapped at the bottom of a pond--the memory of a promise I made sometime last year, a promise I was sure would never be fulfilled. A promise that doesn't have room in our budget at present.
Well, the clean room has been going strong for 8 days now with no signs of stopping. Professor and Lion are more than a little proud that their room is the cleanest room in the house.
I'd better start checking Ebay.