As was previously posted try biddingfortravel BUT the hotels by Disney are rated Resort not 5*. Hotels that come up include Marriot World center but also the Hilton (DTD), Wyndham (DTD), Swan/Dolphin (not very often) and Gaylord Palms. You can't control which hotel you get. DON'T BID IF YOU WON'T BE HAPPY WITH ANY OF THE HOTELS.
Basically a free-rebid is when you add a zone that doesn't offer a resort hotel. You've increased your bid but will only get a hotel in your original zone.