Shion

Shion is a free, full-featured home automation application for the Mac (10.4+). Using Shion.app, you can control and monitor a variety of X10 and INSTEON devices from the convenience of your Mac computer.

Shion.app also includes Snapshots, an easy way to configure & manipulate multiple devices with a single click. Shion.app's Triggers let Shion monitor and respond to changes in it's local environment: time of day, sunrise & sunset, temperature changes, and more.
Shion.app is available for no cost, and is designed to work with the forthcoming Shion Online subscription service that allows your to monitor and control your environments from anywhere in the world.