Inverarity writes in regarding serial port projects for PCs – “There’s a great book for this stuff, Controlling the World with your PC, by Paul Bergsman. I loved this book when I was a young tinkerer (alas I have much less time for tinkering these days, which is why I live vicariously through Makezine.) Mr. Bergsman also used to write for Circuit Cellar, I think. The book has general tips for interfacing with the parallel port, as well as designs for driving LEDs, relays, stepper motors, and lots of other stuff. Great fun!” Link.
HOW TO – Controlling the World with your PC