Updated 2014-10-02 to version 3. Versions 1 and 2 likely don't work on modern versions of the Arduino platform.
This is a design for an Arduino-based 8-channel thermocouple datalogger. It makes use of an Analog Devices AD595 thermocouple amplifier that works with type K and type T thermocouples. The 8 thermocouple channels are routed through a ADG407B differential multiplexer and fed into the AD595 amplifier. Data are saved to a SD card, and a real time clock provides time keeping abilities.
You will need the SdFat library from https://github.com/greiman/SdFat and the RTClib library from https://github.com/mizraith/RTClib to use version 3. The Wire, SPI, and LiquidCrystal libraries should come with the stock Arduino software.
The design and hardware are described here: http://lukemiller.org/index.php/2010/08/a-thermocouple-datalogger-based-on-the-arduino-platform/