Interface?

I have figured out where I am going to buy most of the stuff for building a sim, but there is one huge thing I am unsure of. That is that I don't know what to use for interfacing, or even what to do, and how to use interfaces. Can someone help me understand this more, and recommend a good interface card that is cheap and easy to use?

Thanks in advance. :D
Alex

What kind of functions are you planning on implementing? Simple stuff like landing light, gear, nav, and beacon light switches or more complex like gauges, heading, and course knobs etc;

I am looking to interface the whole MIP, Overhead, and Pedestal. No, I don't have any of this yet, I just want to know how to do it for future reference.

Thanks in advance:D
Alex

FDS interface, Opencockpits, phidgets.