Several people are starting to work on having RepRap make electronics. This includes, of course, making its own circuitry. For example, I'm pleased to say that this blog post itself is rather eclipsed by Johnny Russell's beautifully neat Arduino Mega Shield made in a RepRap here I have been integrating PCB production into the RepRap software to try to make it as straightforward as possible. I've used the results to make these:which you can see fully-assembled at the top of this post. They (together with an Arduino Mega) are a full set or RepRap electronics that you can make in the machine itself. It's all described here.

The software is, needless to say, rather experimental. It is described here. When it's been tested a bit more, we'll do another release with it in. In the meantime, it's all in the latest code in the RepRap Subversion Repository