Networking multiple Arduino using digital I/O pins

Hi. I'm currently working on a project involving multiple discreet modules each running an arduino uno and I want these modules to be able to communicate using a maximum of 8pins. The reason for the 8pin limit is that I was thinking of using a standard UTP/lan cabel.

One module is the master and the rest are the slaves. The master communicates bidirectional with the slaves, but the slaves never communicates among them self. The easy solution would be to run one cable from the master to each slave, but I want to limit the use of pins on the master to just 8 as well so I'm gonna go for the solution of daisy chaining all the modules and using parallel communication. So I now need a protocol for writing and reading data from and to the master and the salves using only 8 digital pins in total.

The kind of data I want to transmit or more or less function ID's and the current values for those functions. Something like: Device 15, function 3, value 1;

Whats is the best way of doing this? I'm very grateful for any kin of input.

Whats is the best way of doing this?

Use RS485 drivers and protocol. You will only need two signal wires. http://en.wikipedia.org/wiki/RS-485

Thanks for an quick answer.

You don’t happen to know of a good “how to” guide for Arduino?

No, there is always google.