We have the same routine as mmiller711 - $5/day, left in the morning before we leave for the parks ( I put it under the little card that says "your room was cleaned by...). We had an interesting experience on our trip this past December. Our son got sick one night, so our usual routine of being up and out by 7:30 was broken as we slept in. When we left our room, our "mousekeeper" was down the hall. She rushed over to see if everything was alright! She told us that she was worried when we hadn't left early, and that she would clean the room right away so that it would be ready when we came back for DS nap. I was amazed at what close attention she paid (I was also relieved that we're pretty neat people, and never leave the room a mess - hehehe).
Especially considering that I would pay $50 - $100 to somebody to clean my house, I think a couple of bucks a day is a nice small way to say thanks. 

