For past few days, I have been working on a PIC12F683 based temperature data logger. I just finished this project and the product is available on my PIC12F683 blog page.This is how the finished product looks like.
It reads temperature values from a DS1820 sensor and stores in its internal EEPROM. It has 3 selectable sampling intervals (1 sec, 1 min, and 10 min). Three tact switches provides 7 functions, and this runs with 3 AAA batteries. It can be interfaced to a PC through serial port, and also has an ISCP header for firmware upgrade.