homemade cleaner for basic drip coffee maker Is it possible to create a cleaning agent to use on a basic drip coffee maker using household items? If so, what ingredients are needed and in what ratios? 

I am mostly concerned with cleaning the insides that I believe are made from plastic. The carafe I can clean separately. I know that there are products on the market, but I am interested in homemade solutions.
Ordinary white vinegar works just fine, but the smell bothers some people. If so, use citric acid. You can either pick some up at your local grocer, or order it by the pound. I use about a tablespoon to a quart for descaling. It's gentle, has little or no odor (you may smell gasses released by the dissolved scale however), and safe unless you get it in your eyes.