For the past few months, just about once a week, 2 very nice ladies who are Jehovah's Witnesses have been coming to my door.  It makes me very uncomfortable.  I respect everyone's right to their religious convictions and expect the same.  When the show up at my home, it feels like an invasion of my privacy as well as a lack of respect for my right to my religious convictions as I would assume they likely want to "convert" me.
I am polite to a fault and really don't to know how to deal with this.  This morning, I noticed their car in the driveway so knew who was at the door and just didn't answer.  
Does anyone have any thoughts on this?  What is the best way to discourage these visits?