How to display extended ASCII characters, e.g., the standard degree symbol, DEC 167, on the Serial Monitor [not LCD]?
The Arduino serial monitor uses UTF-8, per the discussion at http://forum.arduino.cc/index.php?topic=172814.0 -- 

For the U+00B0 degree symbol, you'd send the bytes UTF8 0xC2 0xB0 like this:

Serial.print("°");