Hi,
if you use Arduino Mega (128/256) or like to connect with other Arduino you may consider to use Data Logger Shield v 1.0 (http://pcb.daince.net/doku.php?id=data_logger) available on ebay.
I use it for many different temperature measuring and logging project. It is available in different configuration depends of needs. For temperature measuring depends what you measure, but in my case I use Maxim IC 1-wire DS18B20.
Best regards
Dubravko Penezic