Guys you might think I'm nuts but there is a drain unclogger called a drain king. You can buy them at most hardware stores. They go on the end of a garden hose and slip down the drain. When you turn on the garden hose the drain king swells and plugs up the end of the pipe. You can hear it "Hammering" as it unclogs the drain. One piece of advice. Ir you're trying to unclog a drain upstairs make sure it doesn't fill up your lower level with water. My house has PVC pipes and it has worked for me every time. Here is a link to what it looks like.
http://www.idealtruevalue.com/servlet/the-47027/Detail