Arduino House Alarm???

I am working on a house alarm and using the Arduino system. I am looking for door switches or contacts to monitor the state; open or closed. Does anyone know of any? Nothing too fancy trying to keep cost down. Thanks Jose in Denver Colorado!

Why not use real alarm switches and reed switches?

Where does one purchase these items?? Venders websites etc…??

http://www.google.co.uk/search?hl=en&q=%22Reed+switches%22+Denver+&meta=&aq=f&oq=