programmerml -
I have been doing Home Automation for about 15 years, so I will try to give you a snapshot of info and help you out. I agree with everything cr0sh has said...
When you are working with Home Automation there are basically two types of automation. Ad-hoc communication meaning a few devices with a remote to control them, and having a centralized controller.
Since you want to be able to control you devices from you iPod touch, you would most likely need to look to the centralized controller model. That means one central point that knows the status of all of your "devices" (switches, lights, etc...) and how to communicate to them. You would also need to find one with a built in web interface (so you iPod can control it).
Nowadays, most people run software on a computer to act as this centralized home automation controller. This HA controller runs software to monitor the states of the devices, provides a UI for controlling them, allows you to trigger events, and has physical hardware interface so it can communicate to the devices. (For example a special cable that goes from a serial port to a wall jack can allow the server to control X-10 devices).
So there are two ways for you to start -
(A) buy a "starter kit' with a few controllable switches/outlets and a remote control unit. While this wouldn't initially allow you to leverage your iPod, you could later expand the system, and add a home controller with a web interface.
(B) read some review of various home automation software programs and try a few. Most of them have built in web interfaces, which would allow you to control you "devices" from the web browser in your iPod Touch.
All of my experience is with a program called Homeseer, which has a huge community of users/hobbyists who work with it (very similar to the Arduino community). You can download a free trial of HomeSeer here Smart Home Automation Software Downloads | HomeSeer
Once you have picked out a program, you need to decide which Home Automation Technology you want to use. The original HA products used a technology called X-10. These devices still exist (and work) today, and you can often find them very cheap on eBay. You might even be able to buy a starter package consisting of a home automation program, computer interface, and a few controllable switches for a decent price.
Once you learn more about HA, you will discover that there are lots of competing standards each with their pros/cons. You can also design custom circuits (like ones based on Arduino) and integrate them into your Home Automation system via a serial connection (or even Xbee)
The first place I would start is to start reading forums dedicated to Home Automation. It will be a much better place to get information. The HomeSeer forums can be found here (even though some parts are specific to their software, much of it is great general HA information): http://board.homeseer.com/
I hope this helps get you going in the right direction.