Andrew Liszewski of OhGizmo! suspects that the Snakeliner Presidential Suite may be the most extravagant travel trailer on the market. When fully expanded, its 969 square feet of space include a waterbed, central heating, and a whirlpool. That's the base model, priced at $930,000. If you're able and willing to spend more, you can get options like a helicopter landing site and a motorboat in the cellar. Note that it probably can't be hauled by a bicycle.
Link via OhGizmo!