What is the most common home automation technology?
Here are the most common technologies/protocols based on my experience purchasing devices:


Zwave: proprietary, wireless, and tons of devices available
Insteon: Uses power lines and a wireless radio for redundancy (dual-band)
ZigBee: Wireless, but shares the same spectrum as cordless phones, microwaves, etc. But you can purchase ZigBee chips without having a OEM license, so that can mean cheaper in some instances


Also, keep an eye on enOcean devices that will be getting cheaper and cheaper. They are used mostly in larger corporate buildings right now, but that could change as controller prices come down.

As far as getting started, you need some sort of controller to interface with all your devices. Have a look at MiCasVerde controller which connects to zwave devices (and many Insteon devices if you buy an additional plug component). That gives you tons of devices to interface with, but mostly on the lighting, temperature, door-locks, etc. Setting it up for controlling TV and fridge would not be trivial.

Hope that helps!