The best I been able to do with any reliability is about 85 feet using RS232 and one of the MAX inverter chips. The extra chip is to generate true RS232 voltages in this case.

The standard for RS232 will swing from -12volt to +12 volt. The PICs running on 5 volts work fine as do most of the computers that have a serial port with a +/-5 volt swing(have not seem a true voltage level for some time) for maybe 50 feet with good cable.

The 7805 would also work to power the nodes.