What is the tip for weekly housekeeping at a hotel?

I'm staying in an efficiency hotel for a month. Once a week, housekeeping is included. They change the sheets and put down new towels. I think they vacuum too. It's not a fancy hotel. The room rate is about $50/night. What would be the appropriate tip for the housekeeper, if any.

i wouldnt give them anything. they probably wouldnt take money that you left out for them, stealing (hint hint).

The appropriate amount is 2 dollars a day. :) http://answers.yahoo.com/question/accuse_write?qid=20080822080818AANuojP&kid=B7tUOGy.VXASGtqGyKr6&s=comm&date=2009-03-18+15%3A32%3A56&.crumb=