I've started down that road with Philips Hue lights. Admittedly expensive, but nice and I can build up the system over time. They're Zigbee and Philips are very very open with them. Incidentally they do the best warm-white I've ever seen in an LED bulb, which is nice.

I'm actually looking at one of the Hue Tap switches now; they're a battery-less switch (kinetic power) with three buttons (I think) that you can customize. So I can, for example, put one in my bedroom and have a button on it that turns all the lights off in the house for when I'm about to go to sleep, etc. No need to run cables through walls and have switches where you want.