Not sure if this has been posted yet but stumbled upon a new hotel booking engine today called PointsHound. Basically it lets you earn United, Delta, Hawaiian, or Aeromexico miles for every hotel reservation you make. Granted I wouldn't use this to book stays where you are wanting to earn SPG, Hyatt, or any other loyalty points but places like Las Vegas work great. A $500 stay at New York New York that you were going to make anyway will earn you 1200 United miles. The more hotels you book the more you earn. You start off at 4x miles, then 6x, and up to 9x.