I have seen a few projects over the years that people have done. Mostly, it is just used to get more sensor data into your system. I saw one project where a guy with a watercooled PC added fan speed sensors, water pump speed, water temperature, and a few other voltage sensors. Even if your motherboard doesn't have a SMBlink or Infolink header, you can add one easily. All you have to do is trace down the I2C lines on a RAM chip, then follow it down to the DIMM socket, locate the solder points on the backside of the motherboard, then solder in a connector to add your sensor devices.

Rayer's SMB tool can reprogram the clock chip of some BX boards on the fly allowing hot switching of FSB speed.