Model Railroad Signals and How to Get Started
Here is a page that explains some signal basics and how to get started, and other things to consider.
Links are also given for the different hardware that is available, from the simple to the full featured.
A Modular System for Mounting Your Signals.
Afraid that you will have to crawl under your layout and solder or screw all those tiny signal
wires to a circuit board? Here is a nice way of making the mounting modular.
An LED Switch Lamp
Make a simple working switch lamp using some bits of plastic and a bi-polar LED.