One of the simplest methods of interfacing a thermocouple to 8051 microcontroller is 1-wire technology ..
Here is an example of an IC which will take signal form J-thermocouple, condition it and convert it to digital form that can be read by a microcontroller: **broken link removed**
If you need more information on 1-wire devices goto this site:
**broken link removed**
Regards,
IanP