If you're bored with staying in cookie-cutter hotels on vacation, how about lodging in a sphere in the Canadian woods, a refurbished plane in Costa Rica or the "Onion House" in Hawaii? Not only will you have unique stories to tell, but you may also save money. "Many people don't realize they can rent a castle or a windmill loft for less than a hotel stay," says TJ Mahony, founder of FlipKey, a vacation travel site majority-owned by TripAdvisor. Mahony says such rentals tend to be, on average, 50 percent cheaper than hotels. Here's a selection of unique accommodations from Flipkey.com.