Good resources to learn about Home Automation
There's no definitive resource on the topic or at least I could not find one (and I spent couple of months heavily involved in HA during one of my projects). 

Get started with the Wikipedia article on HA. This gives you overview of what is what and gives you a good starting point. Then proceed to familiarise yourself with technology out there like X10, UPB, Z-Wave, etc etc. 

From there you will be able to start to judge the prices of different technologies as well as find resources on specific tech/protocol/brand which seems to be a little more common than broad scope resources. In terms of sourcing the components, eBay as always is a good starting point. I ordered a few things from New Zealand because availability here is shocking. Though always be aware of country differences (voltages, frequencies, etc.)

I hope this helps you to get started. And I will definitely keep an eye on answers here - maybe I have missed something too.