Right now most suppliers have plenty of inventory for the peak booking seasons in the USA (which is May to September). Many USA suppliers are temporarily marking down there base rental rates to get reward early bookers for the 2010 RV'ing season
You find plenty of other rv specials ranging heavy discounts on 15+ days booking, free days available, one way rental rental deals, free kits and mileage.
Another note for international travellers - save yourself disappointment and book your motorhome before you book your flight to the USA. Unlike flights, motorhomes do not have the same flexibility and availability!