Featherboards are a quick functional project that you can make out of any scrap you have around the shop.
A featherboard is easily constructed from a piece of wood roughly 8" to 12" long and 2" to 3" wide. Make a diagonal cut along one end, and cut parallel slots starting at the diagonal end in towards the flat side, around 3" to 4" long. Make the slots about 1/8" apart, and smaller if you are able.
Using a featherboard is as simple as clamping it to your work fence with the "fingers" pointing down like a hold-down clamp, or clamp it to the table itself to hold your workpiece against a blade or fence.
The idea behind the featherboard is to use it to apply constant pressure on your workpiece to hold it against the fence or table, often closer to the blade than your real fingers would find safe. Adjust the pressure so that your workpiece is being pressed slightly by the featherboard, but not so tightly that you have to force the workpiece through. Also, clamp the featherboard so the workpiece is being passed along the fingers, towards the point that you cut by your diagonal.
Of course, if you have no desire to manufacture yourself featherboards, you can purchase commercial featherboards from a number of suppliers. These have more bells and whistles than you are likely to put into your own featherboard, but they can be helpful.