I2C is a simple communications bus similar to 1-wire, which we’ve talked about earlier. [hnch] has built a really simple I2C parallel port interface. It’s optically isolated so you don’t have to worry about a mistake frying your computer. I2C modules already come with the Linux kernel. It will even treat temperature sensors you attach exactly like the ones you have on your motherboard so you can monitor them using ordinary software like gkrellm. There are lots of other devices that use I2C as well. [hnch] has a nerdity gallery and will gladly write up any other project you’d like information on.