You can/could also find Coffee HOWTO in your distro's HOWTO package. (I found a reference back to v0.5 of the document in 1998.)

Has simple schematics to get you started for the hardware, using the parallel port to toggle relays.

It's a very neat little document, and inspired me to write a simple kernel module so I could echo 1 | sudo tee /sys/whatever/coffee0 to turn pin 0 high on the parallel port. (This is silly, and it's much easier to just do things in user space!)