Hi there,
Not sure where your talking about mounting.... but for my primary indoor sensor, I mounted a non-board mounted DS1820 inside my HVAC thermostat housing.  I then calibrated the DS1820 to the temp shown on the thermostat.  That way I was able to run the sensor wiring in the same wire hole for my thermostat.  No wires showing  
 
  
For other rooms, I went to Radio Shack and bought plastic project boxes and used a Dremel to drill vent holes (which I covered with black open mesh foam).  I drilled a cable hole in the back of the case and then through the wall.  No wires showing.  However, the Hobby Boards version looks much better.  
The basement just has a dangling DS18S20 with heat shrink covering the wires.  
If your talking outside.....  Completely different animal.  You can spend as much as you are willing to spend for a radiation shield or use what you dig up around the house.  One fellow's example was a blob of silicone surrounded by heat shrink hanging under the front eave of his house.
Good luck!
Steve