Earlier today I had the privilege of sitting in on Scott Sheppard's Inside Mac Radio broadcast. I had a great time talking about home automation using Mac OS X. An archive of the show will be up soon, for on-demand listening.
Here are some links for the products mentioned during the show:
XTension by SandHill Engineering
Indigo by Perceptive Automation
WeatherMan by AfterTen Software
If you need an X10 starter kit or modules, visit Smarthome, Inc.