Here I discuss the power system I used for this project. It's pretty simple and short.
The PWM pin/signal, pin 2.1, is tied into the input or digital side of the solid state relay. The solid state relay takes a digital signal as an input that turns on some really big power FETS on the AC side. This is usually accomplished by using optical isolation. That means that your digital side can be isolated form your analog or AC side. Allowing you to use a very small input to control a very large output without any coupling problems.
The output of the SSR connects and disconnects the hot line from a 110 outlet to the toaster. So, when the pulse is high, the output of the SSR is on and connecting the AC power into the toaster. When the pulse is low, the SSR is off, disconnecting the toaster from 110. The other two lines, earth ground and neutral, are tied together on a terminal block. These can always stay connected so this was a simple and cheap solution.
That is pretty much it for the power system! As I said, it is very simple, but I don't recommend you ever work with 110 and definitely never while it is live!
Note-I haven't been able to get the python app packed up as an exe yet because of some technical problems, but when I get this figured out I'll update the package. The source code (python GUI and embedded C) is packed up as the aptana project and CCS studion project respectively. It should be simple to import these and check out the code. If importing doesn't work just check out the source files or create your own project and add the source files only to it.