Thanks for the responses. Topic about protecting DS18B20 is also mine 
About size of one wire code for DS18B20 -- yes, I use ATmega8 and this is an issue.
What about using internal reference voltage will it work from batteries? I've found example in the comments to posts you mentioned, I need to check ATMega8 datasheet it reference voltage as far as I remember is different from ATmega168 and ATmega328...
update:
http://www.arduino.cc/en/Reference/AnalogReference
INTERNAL: an built-in reference, equal to 1.1 volts on the ATmega168 or ATmega328 and 2.56 volts on the ATmega8 (not available on the Arduino Mega)